diff --git a/.idea/workspace.xml b/.idea/workspace.xml
index 2992a5b..07e07cd 100644
--- a/.idea/workspace.xml
+++ b/.idea/workspace.xml
@@ -4,7 +4,7 @@
     <option name="autoReloadType" value="SELECTIVE" />
   </component>
   <component name="BackendCodeEditorMiscSettings">
-    <option name="/Default/Environment/Hierarchy/GeneratedFilesCacheKey/Timestamp/@EntryValue" value="4" type="long" />
+    <option name="/Default/Environment/Hierarchy/GeneratedFilesCacheKey/Timestamp/@EntryValue" value="3" type="long" />
     <option name="/Default/Environment/UserInterface/HierarchyView/ViewStyle/@EntryValue" value="SuperTypes" type="string" />
     <option name="/Default/Housekeeping/FeatureSuggestion/FeatureSuggestionManager/DisabledSuggesters/=SwitchToGoToActionSuggester/@EntryIndexedValue" value="true" type="bool" />
     <option name="/Default/Housekeeping/LiveTemplatesHousekeeping/HotspotSessionHintIsShown/@EntryValue" value="true" type="bool" />
@@ -23,11 +23,18 @@
     <generated>
       <config projectName="exercises" targetName="dsa__ch2_linear_list__dsa_0205_polynomial_addition" />
       <config projectName="exercises" targetName="cs101__stage_2__dh_11_03_jump_rope" />
+      <config projectName="exercises" targetName="dsa__ch5_binary_tree__dsa_0514_heap" />
       <config projectName="exercises" targetName="pojcs101_T12559_biggest_smallest_combination_WRONG" />
       <config projectName="exercises" targetName="cs101__stage_1__dh_05_02_three_nums" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_14_05_flip_words" />
       <config projectName="exercises" targetName="pojcs101_M02694_polish_notation_tree" />
       <config projectName="exercises" targetName="pojcs101_M01017_6_boxes" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_16_01_shit_pair_nums" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_14_03_linear_equations_COMPLICATED" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_15_03_courage_machine" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_15_08_matrix_modification" />
       <config projectName="exercises" targetName="cs101__stage_1__dh_05_05_pair_of_shit_nums_SIEVE" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_16_07_observer_stone" />
       <config projectName="exercises" targetName="dsa__ch3_stack_queue__dsa_0301_sliding_window_SLOW" />
       <config projectName="exercises" targetName="luogu_ez_B3628" />
       <config projectName="exercises" targetName="dp__TJOI2007_walk_segments_dp" />
@@ -44,6 +51,7 @@
       <config projectName="exercises" targetName="dsa__ch4_string__luogu_template_kmp_P3375" />
       <config projectName="exercises" targetName="pojcs101_M02431_cows_gas_leak_WRONG" />
       <config projectName="exercises" targetName="cs101__stage_1__dh_05_03_different_num" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_16_03_arrange_activities" />
       <config projectName="exercises" targetName="luogu_P1160_biodir_linked_list" />
       <config projectName="exercises" targetName="pojcs101_E01003" />
       <config projectName="exercises" targetName="JLOI2009_binary_tree" />
@@ -52,18 +60,26 @@
       <config projectName="exercises" targetName="dsa__ch2_linear_list__dsa_0203_string_insertion" />
       <config projectName="exercises" targetName="cs101__stage_pre__dh_00_16_swap_bits" />
       <config projectName="exercises" targetName="pojcs101_T27373_biggest_combination_t2_TLE" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_14_06_number_systems" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_15_01_is_abbr" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_16_06_line_wrap" />
+      <config projectName="exercises" targetName="dsa__ch5_binary_tree__dsa_0514_heap_STL" />
       <config projectName="exercises" targetName="pojcs101_M02524_ubiquitous_religions_dsu" />
       <config projectName="exercises" targetName="dsa__ch5_binary_tree__dsa_0510_reconstruct_tree" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_16_02" />
       <config projectName="exercises" targetName="cs101__stage_pre__dh_00_15_jusephus" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_15_02_tiny_kmp" />
       <config projectName="exercises" targetName="exercises" />
       <config projectName="exercises" targetName="dp__SHOI2002_ski_dp" />
       <config projectName="exercises" targetName="pojcs101_M01852_ants_falling" />
       <config projectName="exercises" targetName="cs101__stage_1__dh_01_04" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_14_02_special_location" />
       <config projectName="exercises" targetName="cs101__stage_1__dh_06_04_split" />
       <config projectName="exercises" targetName="dsa__ch2_linear_list__P2629_good_news" />
       <config projectName="exercises" targetName="cs101__stage_1__dh_03_04_lamps" />
       <config projectName="exercises" targetName="cs101__stage_1__dh_03_03" />
       <config projectName="exercises" targetName="dsa__ch3_stack_queue__dsa_0302_calculator_WRONG" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_15_06_pass_balls" />
       <config projectName="exercises" targetName="pojcs101_T27104_chicken_monitors" />
       <config projectName="exercises" targetName="dsa__ch4_string__dsa_0406_valid_string" />
       <config projectName="exercises" targetName="NOIP2016J_bay" />
@@ -80,7 +96,6 @@
       <config projectName="exercises" targetName="cs101__stage_2__dh_11_01_change" />
       <config projectName="exercises" targetName="pojcs101_M01328_radar_greedy_WRONG" />
       <config projectName="exercises" targetName="dp__backpack_dp__NOIP2005J_herbs_dp_knapsack" />
-      <config projectName="exercises" targetName="cs101__stage_2__dh_12_04_day_delta" />
       <config projectName="exercises" targetName="dsa__ch2_linear_list__dsa_0202_card_stacking" />
       <config projectName="exercises" targetName="cs101__stage_1__dh_03_05_perfect_cubes" />
       <config projectName="exercises" targetName="pojcs101_M02692_12_coins" />
@@ -90,23 +105,30 @@
       <config projectName="exercises" targetName="cs101__stage_1__dh_01_03" />
       <config projectName="exercises" targetName="pojcs101_E02883" />
       <config projectName="exercises" targetName="dsa__ch2_linear_list__dsa_0217_magic_square" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_12_04_date_delta" />
       <config projectName="exercises" targetName="cs101__stage_2__dh_11_02_shit_num" />
       <config projectName="exercises" targetName="dsa__ch4_string__dsa_0404_string_loop" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_15_07_char_stat" />
       <config projectName="exercises" targetName="dp__backpack_dp__NOIP2005J_herbs_dp_knapsack_MWASTE" />
       <config projectName="exercises" targetName="dp__backpack_dp__NOIP2006S_jinming_budget_dp_knapsack" />
       <config projectName="exercises" targetName="dp__backpack_dp__NOIP2005J_herbs_dp_knapsack_PINGPONG" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_14_01_day_of_date" />
       <config projectName="exercises" targetName="JLOI2009_binary_tree_GIVEUP" />
       <config projectName="exercises" targetName="dsa__ch3_stack_queue__dsa_0306_stack_operation" />
       <config projectName="exercises" targetName="cs101__stage_2__dh_12_03_tumor_detection" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_14_04_eat" />
       <config projectName="exercises" targetName="pojcs101_M03704_brackets" />
       <config projectName="exercises" targetName="pojcs101_M03441_sum_zero" />
       <config projectName="exercises" targetName="pojcs101_M01328_radar_greedy" />
       <config projectName="exercises" targetName="pojcs101_M02746_josephus_problem_simulation" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_15_04_related_months" />
+      <config projectName="exercises" targetName="cs101__2023mid__exam_2023mid_05_mask" />
       <config projectName="exercises" targetName="cs101__stage_2__dh_13_01_max_points_WRONG" />
       <config projectName="exercises" targetName="cs101__stage_2__dh_12_06_big_binary_addition" />
       <config projectName="exercises" targetName="dsa__ch3_stack_queue__USACO12MARs_flowerpot_WRONG" />
       <config projectName="exercises" targetName="dsa__ch2_linear_list__dsa_0204_prefix_cycle" />
       <config projectName="exercises" targetName="NOIP2003J_bigint" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_15_05_clinic_queue" />
       <config projectName="exercises" targetName="pojcs101_M01922_ride_follower" />
       <config projectName="exercises" targetName="luogu_template_dsu_P3367" />
       <config projectName="exercises" targetName="dsa__ch3_stack_queue__dsa_0302_calculator" />
@@ -129,6 +151,7 @@
       <config projectName="exercises" targetName="cs101__stage_pre__dh_00_05_sum_fractions" />
       <config projectName="exercises" targetName="_others__jzh__jzh_e2_j" />
       <config projectName="exercises" targetName="dsa__ch2_linear_list__dsa_0201_dictionary" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_14_03_linear_equations" />
       <config projectName="exercises" targetName="dsa__ch3_stack_queue__dsa_0301_sliding_window" />
       <config projectName="exercises" targetName="dsa__ch3_stack_queue__USACO12MARs_flowerpot" />
       <config projectName="exercises" targetName="pojcs101_T01011_sticks_WRONG" />
@@ -142,6 +165,7 @@
       <config projectName="exercises" targetName="cmake-build-debug-gcc__CMakeFiles__4.3.1__CompilerIdCXX__CMakeCXXCompilerId" />
       <config projectName="exercises" targetName="dp__eagle_egg" />
       <config projectName="exercises" targetName="lc_135_candy" />
+      <config projectName="exercises" targetName="cs101__stage_2__dh_16_08_tianji_horse" />
       <config projectName="exercises" targetName="cs101__stage_1__dh_05_04_fried_chicken" />
       <config projectName="exercises" targetName="cs101__stage_1__dh_04_01_fibonacci" />
       <config projectName="exercises" targetName="dsa__ch4_string__dsa_0403_within_string" />
@@ -153,29 +177,35 @@
     <configurations />
   </component>
   <component name="ChangeListManager">
-    <list default="true" id="4491295e-723c-4e0b-b7b4-9be1cbde5db8" name="更改" comment="some programs!!!">
-      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_12_01_variance.cpp" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_12_02_count_chars.cpp" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_12_03_tumor_detection.cpp" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_12_04_day_delta.cpp" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_12_05_iter_hui.cpp" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_12_06_big_binary_addition.cpp" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_13_01_max_points.cpp" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_13_01_max_points_WRONG.cpp" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_13_02_tumor_again.cpp" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_13_05_books.cpp" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_13_06_nums_in_string.cpp" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/dsa/ch4_string/dsa_0403_within_string.cpp" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/dsa/ch4_string/dsa_0404_string_loop.cpp" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/dsa/ch4_string/dsa_0406_valid_string.cpp" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/dsa/ch4_string/luogu_template_kmp_P3375.cpp" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/dsa/ch5_binary_tree/dsa_0510_reconstruct_tree.cpp" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/dsa/ch5_binary_tree/luogu_P4715_matches.cpp" afterDir="false" />
-      <change afterPath="$PROJECT_DIR$/dsa/ch5_binary_tree/luogu_T750119_bin_tree_iter.cpp" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/.idea/editor.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/editor.xml" afterDir="false" />
+    <list default="true" id="4491295e-723c-4e0b-b7b4-9be1cbde5db8" name="更改" comment="数算！">
+      <change afterPath="$PROJECT_DIR$/cs101/2023mid/exam_2023mid_05_mask.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_14_01_day_of_date.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_14_02_special_location.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_14_03_linear_equations.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_14_03_linear_equations_COMPLICATED.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_14_04_eat.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_14_05_flip_words.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_14_06_number_systems.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_15_01_is_abbr.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_15_02_tiny_kmp.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_15_03_courage_machine.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_15_04_related_months.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_15_05_clinic_queue.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_15_06_pass_balls.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_15_07_char_stat.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_15_08_matrix_modification.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_16_01_shit_pair_nums.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_16_02.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_16_03_arrange_activities.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_16_06_line_wrap.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_16_07_observer_stone.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_16_08_tianji_horse.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/cs101/stage_2/dh_16_08_tianji_horse_WRONG.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/dsa/ch5_binary_tree/dsa_0514_heap.cpp" afterDir="false" />
+      <change afterPath="$PROJECT_DIR$/dsa/ch5_binary_tree/dsa_0514_heap_STL.cpp" afterDir="false" />
       <change beforePath="$PROJECT_DIR$/.idea/workspace.xml" beforeDir="false" afterPath="$PROJECT_DIR$/.idea/workspace.xml" afterDir="false" />
-      <change beforePath="$PROJECT_DIR$/_others/others_test.c" beforeDir="false" afterPath="$PROJECT_DIR$/_others/others_test.c" afterDir="false" />
       <change beforePath="$PROJECT_DIR$/_others/others_test_cpp.cpp" beforeDir="false" afterPath="$PROJECT_DIR$/_others/others_test_cpp.cpp" afterDir="false" />
+      <change beforePath="$PROJECT_DIR$/cs101/stage_2/dh_12_04_day_delta.cpp" beforeDir="false" afterPath="$PROJECT_DIR$/cs101/stage_2/dh_12_04_date_delta.cpp" afterDir="false" />
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     <option name="SHOW_DIALOG" value="false" />
     <option name="HIGHLIGHT_CONFLICTS" value="true" />
@@ -210,7 +240,9 @@
   <component name="HighlightingSettingsPerFile">
     <setting file="file://$PROJECT_DIR$/_others/others_test.c" root0="FORCE_HIGHLIGHTING" />
     <setting file="file://$PROJECT_DIR$/cs101/stage_1/dh_05_05_pair_of_shit_nums_SIEVE.cpp" root0="FORCE_HIGHLIGHTING" />
+    <setting file="file://$PROJECT_DIR$/cs101/stage_2/dh_12_04_date_delta.cpp" root0="FORCE_HIGHLIGHTING" />
     <setting file="file://$PROJECT_DIR$/cs101/stage_2/dh_13_01_max_points_WRONG.cpp" root0="FORCE_HIGHLIGHTING" />
+    <setting file="file://$PROJECT_DIR$/cs101/stage_2/dh_16_08_tianji_horse_WRONG.cpp" root0="FORCE_HIGHLIGHTING" />
     <setting file="file://$PROJECT_DIR$/dsa/ch3_stack_queue/USACO12MARs_flowerpot_WRONG.cpp" root0="FORCE_HIGHLIGHTING" />
     <setting file="file://$PROJECT_DIR$/dsa/ch3_stack_queue/dsa_0301_sliding_window_SLOW.cpp" root0="FORCE_HIGHLIGHTING" />
     <setting file="file://$PROJECT_DIR$/dsa/ch3_stack_queue/dsa_0302_calculator_WRONG.cpp" root0="FORCE_HIGHLIGHTING" />
@@ -313,6 +345,23 @@
     "CMake 应用程序.cs101__stage_2__dh_13_02_tumor_again.executor": "Run",
     "CMake 应用程序.cs101__stage_2__dh_13_05_books.executor": "Run",
     "CMake 应用程序.cs101__stage_2__dh_13_06_nums_in_string.executor": "Debug",
+    "CMake 应用程序.cs101__stage_2__dh_14_01_day_of_date.executor": "Run",
+    "CMake 应用程序.cs101__stage_2__dh_14_02_special_location.executor": "Run",
+    "CMake 应用程序.cs101__stage_2__dh_14_03_linear_equations.executor": "Debug",
+    "CMake 应用程序.cs101__stage_2__dh_14_04_eat.executor": "Run",
+    "CMake 应用程序.cs101__stage_2__dh_14_05_flip_words.executor": "Run",
+    "CMake 应用程序.cs101__stage_2__dh_14_06_number_systems.executor": "Run",
+    "CMake 应用程序.cs101__stage_2__dh_15_01_is_abbr.executor": "Run",
+    "CMake 应用程序.cs101__stage_2__dh_15_02_tiny_kmp.executor": "Debug",
+    "CMake 应用程序.cs101__stage_2__dh_15_03_courage_machine.executor": "Run",
+    "CMake 应用程序.cs101__stage_2__dh_15_04_related_months.executor": "Run",
+    "CMake 应用程序.cs101__stage_2__dh_15_05_clinic_queue.executor": "Run",
+    "CMake 应用程序.cs101__stage_2__dh_15_08_matrix_modification.executor": "Run",
+    "CMake 应用程序.cs101__stage_2__dh_16_01_shit_pair_nums.executor": "Run",
+    "CMake 应用程序.cs101__stage_2__dh_16_03_arrange_activities.executor": "Run",
+    "CMake 应用程序.cs101__stage_2__dh_16_05_line_wrap.executor": "Run",
+    "CMake 应用程序.cs101__stage_2__dh_16_07_observer_stone.executor": "Run",
+    "CMake 应用程序.cs101__stage_2__dh_16_08_tianji_horse.executor": "Run",
     "CMake 应用程序.dp__TJOI2007_walk_segments_dp.executor": "Run",
     "CMake 应用程序.dp__luogu_U434718_eagle_egg.executor": "Run",
     "CMake 应用程序.dsa__ch2_linear_list__P2629_good_news.executor": "Run",
@@ -327,6 +376,7 @@
     "CMake 应用程序.dsa__ch4_string__dsa_0406_valid_string.executor": "Run",
     "CMake 应用程序.dsa__ch4_string__luogu_template_kmp_P3375.executor": "Run",
     "CMake 应用程序.dsa__ch5_binary_tree__dsa_0510_reconstruct_tree.executor": "Run",
+    "CMake 应用程序.dsa__ch5_binary_tree__dsa_0514_heap_STL.executor": "Run",
     "CMake 应用程序.dsa__ch5_binary_tree__luogu_P4715_matches.executor": "Run",
     "CMake 应用程序.dsa__ch5_binary_tree__luogu_T750119_bin_tree_iter.executor": "Run",
     "CMake 应用程序.dsa__linear_list__dsa_0201_dictionary.executor": "Run",
@@ -408,12 +458,7 @@
       <recent name="$PROJECT_DIR$/graph" />
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-  <component name="RunManager" selected="CMake 应用程序.dsa__ch5_binary_tree__dsa_0510_reconstruct_tree">
-    <configuration default="true" type="CLionExternalRunConfiguration" factoryName="Application" REDIRECT_INPUT="false" ELEVATE="false" USE_EXTERNAL_CONSOLE="false" EMULATE_TERMINAL="false" PASS_PARENT_ENVS_2="true">
-      <method v="2">
-        <option name="CLION.EXTERNAL.BUILD" enabled="true" />
-      </method>
-    </configuration>
+  <component name="RunManager" selected="CMake 应用程序.cs101__stage_2__dh_16_08_tianji_horse">
     <configuration default="true" type="CMakeBoostTestRunConfigurationType" factoryName="Boost Test" REDIRECT_INPUT="false" ELEVATE="false" USE_EXTERNAL_CONSOLE="false" EMULATE_TERMINAL="false" PASS_PARENT_ENVS_2="true" TEST_MODE="SUITE_TEST">
       <method v="2">
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@@ -464,6 +509,11 @@
         <option name="com.jetbrains.cidr.execution.CidrBuildBeforeRunTaskProvider$BuildBeforeRunTask" enabled="true" />
       </method>
     </configuration>
+    <configuration default="true" type="CMakeRunConfiguration" factoryName="Application" REDIRECT_INPUT="false" ELEVATE="false" USE_EXTERNAL_CONSOLE="false" EMULATE_TERMINAL="false" PASS_PARENT_ENVS_2="true">
+      <method v="2">
+        <option name="com.jetbrains.cidr.execution.CidrBuildBeforeRunTaskProvider$BuildBeforeRunTask" enabled="true" />
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+      <item itemvalue="CMake 应用程序.cs101__stage_2__dh_16_02" />
+      <item itemvalue="CMake 应用程序.cs101__stage_2__dh_16_03_arrange_activities" />
+      <item itemvalue="CMake 应用程序.cs101__stage_2__dh_16_06_line_wrap" />
+      <item itemvalue="CMake 应用程序.cs101__stage_2__dh_16_07_observer_stone" />
+      <item itemvalue="CMake 应用程序.cs101__stage_2__dh_16_08_tianji_horse" />
       <item itemvalue="CMake 应用程序.cs101__stage_pre__dh_00_05_sum_fractions" />
       <item itemvalue="CMake 应用程序.cs101__stage_pre__dh_00_10_smaller_numbers" />
       <item itemvalue="CMake 应用程序.cs101__stage_pre__dh_00_12_bottle_exchange" />
@@ -1232,6 +1424,8 @@
       <item itemvalue="CMake 应用程序.dsa__ch4_string__dsa_0406_valid_string" />
       <item itemvalue="CMake 应用程序.dsa__ch4_string__luogu_template_kmp_P3375" />
       <item itemvalue="CMake 应用程序.dsa__ch5_binary_tree__dsa_0510_reconstruct_tree" />
+      <item itemvalue="CMake 应用程序.dsa__ch5_binary_tree__dsa_0514_heap" />
+      <item itemvalue="CMake 应用程序.dsa__ch5_binary_tree__dsa_0514_heap_STL" />
       <item itemvalue="CMake 应用程序.dsa__ch5_binary_tree__luogu_P4715_matches" />
       <item itemvalue="CMake 应用程序.dsa__ch5_binary_tree__luogu_T750119_bin_tree_iter" />
       <item itemvalue="CMake 应用程序.graph__ECNA2001_sort_letters" />
@@ -1290,14 +1484,195 @@
   "profileIdByStamp": [
     {
       "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序._others__others_test",
+        "##RUN_CONFIGURATION##": "CMake 应用程序.dsa__ch3_stack_queue__dsa_0301_sliding_window",
         "cmake": "CMakeBuildProfile:Debug-GCC"
       },
       "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
     },
     {
       "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序.dsa__ch3_stack_queue__dsa_0301_sliding_window",
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_15_05_clinic_queue",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.dsa__ch3_stack_queue__dsa_0301_sliding_window_SLOW",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_14_06_number_systems",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_13_02_tumor_again",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_14_04_eat",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.dsa__ch4_string__dsa_0406_valid_string",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_13_01_max_points",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_15_04_related_months",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.luogu_P1160_biodir_linked_list",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.dsa__ch3_stack_queue__dsa_0302_calculator",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.dsa__ch3_stack_queue__USACO12MARs_flowerpot",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_16_08_tianji_horse",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.pojcs101_T27373_biggest_combination_t2",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_14_03_linear_equations",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "Python.dh_04_04_balloons_init1"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.dsa__ch4_string__luogu_template_kmp_P3375",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.dp__TJOI2007_walk_segments_dp",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_15_03_courage_machine",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_16_01_shit_pair_nums",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_15_08_matrix_modification",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_11_03_jump_rope",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_16_07_observer_stone",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序._others__jzh__jzh_c1_h",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.pojcs101_M02746_josephus_problem_simulation",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.NOIP2003J_bigint",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序._others__others_test_cpp",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序._others__others_test",
         "cmake": "CMakeBuildProfile:Debug-GCC"
       },
       "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
@@ -1318,7 +1693,7 @@
     },
     {
       "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序.dsa__ch3_stack_queue__dsa_0301_sliding_window_SLOW",
+        "##RUN_CONFIGURATION##": "CMake 应用程序.dsa__ch5_binary_tree__dsa_0514_heap_STL",
         "cmake": "CMakeBuildProfile:Debug-GCC"
       },
       "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
@@ -1346,14 +1721,7 @@
     },
     {
       "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_13_02_tumor_again",
-        "cmake": "CMakeBuildProfile:Debug-GCC"
-      },
-      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
-    },
-    {
-      "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序.dsa__ch4_string__dsa_0406_valid_string",
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_16_03_arrange_activities",
         "cmake": "CMakeBuildProfile:Debug-GCC"
       },
       "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
@@ -1365,20 +1733,6 @@
       },
       "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
     },
-    {
-      "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_13_01_max_points",
-        "cmake": "CMakeBuildProfile:Debug-GCC"
-      },
-      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
-    },
-    {
-      "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序.luogu_P1160_biodir_linked_list",
-        "cmake": "CMakeBuildProfile:Debug-GCC"
-      },
-      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
-    },
     {
       "first": {
         "##RUN_CONFIGURATION##": "CMake 应用程序.NOIP2016J_bay",
@@ -1393,13 +1747,6 @@
       },
       "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
     },
-    {
-      "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序.dsa__ch3_stack_queue__dsa_0302_calculator",
-        "cmake": "CMakeBuildProfile:Debug-GCC"
-      },
-      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
-    },
     {
       "first": {
         "##RUN_CONFIGURATION##": "CMake 应用程序.pojcs101_T27104_chicken_monitors",
@@ -1416,7 +1763,7 @@
     },
     {
       "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序.dsa__ch3_stack_queue__USACO12MARs_flowerpot",
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_14_05_flip_words",
         "cmake": "CMakeBuildProfile:Debug-GCC"
       },
       "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
@@ -1428,13 +1775,6 @@
       },
       "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
     },
-    {
-      "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序.pojcs101_T27373_biggest_combination_t2",
-        "cmake": "CMakeBuildProfile:Debug-GCC"
-      },
-      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
-    },
     {
       "first": {
         "##RUN_CONFIGURATION##": "CMake 应用程序.JLOI2009_binary_tree",
@@ -1442,25 +1782,12 @@
       },
       "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
     },
-    {
-      "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_12_04_day_delta",
-        "cmake": "CMakeBuildProfile:Debug-GCC"
-      },
-      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
-    },
     {
       "first": {
         "##RUN_CONFIGURATION##": "C/C++ 文件.dh_05_05_pair_of_shit_nums_ANALYSIS.cpp"
       },
       "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
     },
-    {
-      "first": {
-        "##RUN_CONFIGURATION##": "Python.dh_04_04_balloons_init1"
-      },
-      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
-    },
     {
       "first": {
         "##RUN_CONFIGURATION##": "CMake 应用程序.dsa__ch2_linear_list__SDOI2007_queue",
@@ -1468,20 +1795,6 @@
       },
       "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
     },
-    {
-      "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序.dsa__ch4_string__luogu_template_kmp_P3375",
-        "cmake": "CMakeBuildProfile:Debug-GCC"
-      },
-      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
-    },
-    {
-      "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序.dp__TJOI2007_walk_segments_dp",
-        "cmake": "CMakeBuildProfile:Debug-GCC"
-      },
-      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
-    },
     {
       "first": {
         "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_13_06_nums_in_string",
@@ -1498,21 +1811,7 @@
     },
     {
       "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_11_03_jump_rope",
-        "cmake": "CMakeBuildProfile:Debug-GCC"
-      },
-      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
-    },
-    {
-      "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序._others__jzh__jzh_c1_h",
-        "cmake": "CMakeBuildProfile:Debug-GCC"
-      },
-      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
-    },
-    {
-      "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序.pojcs101_M02746_josephus_problem_simulation",
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_15_01_is_abbr",
         "cmake": "CMakeBuildProfile:Debug-GCC"
       },
       "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
@@ -1526,7 +1825,7 @@
     },
     {
       "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序.NOIP2003J_bigint",
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_14_02_special_location",
         "cmake": "CMakeBuildProfile:Debug-GCC"
       },
       "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
@@ -1538,13 +1837,6 @@
       },
       "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
     },
-    {
-      "first": {
-        "##RUN_CONFIGURATION##": "CMake 应用程序._others__others_test_cpp",
-        "cmake": "CMakeBuildProfile:Debug-GCC"
-      },
-      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
-    },
     {
       "first": {
         "##RUN_CONFIGURATION##": "CMake 应用程序.dsa__ch2_linear_list__P2629_good_news",
@@ -1558,9 +1850,23 @@
         "cmake": "CMakeBuildProfile:Debug-GCC"
       },
       "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_15_02_tiny_kmp",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
+    },
+    {
+      "first": {
+        "##RUN_CONFIGURATION##": "CMake 应用程序.cs101__stage_2__dh_14_01_day_of_date",
+        "cmake": "CMakeBuildProfile:Debug-GCC"
+      },
+      "second": "2c1c9069-eeff-46e4-9092-db62e2b1ded5"
     }
   ],
-  "modificationCount": 239
+  "modificationCount": 273
 }]]></component>
   <component name="SharedIndexes">
     <attachedChunks>
@@ -1601,7 +1907,8 @@
     <MESSAGE value="some programs!" />
     <MESSAGE value="some programs!!" />
     <MESSAGE value="some programs!!!" />
-    <option name="LAST_COMMIT_MESSAGE" value="some programs!!!" />
+    <MESSAGE value="数算！" />
+    <option name="LAST_COMMIT_MESSAGE" value="数算！" />
   </component>
   <component name="XDebuggerManager">
     <breakpoint-manager>
@@ -1706,6 +2013,31 @@
           <line>34</line>
           <option name="timeStamp" value="90" />
         </line-breakpoint>
+        <line-breakpoint enabled="true" type="com.jetbrains.cidr.execution.debugger.OCBreakpointType">
+          <url>file://$PROJECT_DIR$/cs101/stage_2/dh_14_03_linear_equations.cpp</url>
+          <line>21</line>
+          <option name="timeStamp" value="94" />
+        </line-breakpoint>
+        <line-breakpoint enabled="true" type="com.jetbrains.cidr.execution.debugger.OCBreakpointType">
+          <url>file://$PROJECT_DIR$/cs101/stage_2/dh_14_06_number_systems.cpp</url>
+          <line>52</line>
+          <option name="timeStamp" value="95" />
+        </line-breakpoint>
+        <line-breakpoint enabled="true" type="com.jetbrains.cidr.execution.debugger.OCBreakpointType">
+          <url>file://$PROJECT_DIR$/cs101/stage_2/dh_15_01_is_abbr.cpp</url>
+          <line>7</line>
+          <option name="timeStamp" value="96" />
+        </line-breakpoint>
+        <line-breakpoint enabled="true" type="com.jetbrains.cidr.execution.debugger.OCBreakpointType">
+          <url>file://$PROJECT_DIR$/cs101/stage_2/dh_15_02_tiny_kmp.cpp</url>
+          <line>46</line>
+          <option name="timeStamp" value="99" />
+        </line-breakpoint>
+        <line-breakpoint enabled="true" type="com.jetbrains.cidr.execution.debugger.OCBreakpointType">
+          <url>file://$PROJECT_DIR$/cs101/stage_2/dh_16_01_shit_pair_nums.cpp</url>
+          <line>48</line>
+          <option name="timeStamp" value="102" />
+        </line-breakpoint>
       </breakpoints>
     </breakpoint-manager>
   </component>
diff --git a/_others/others_test_cpp.cpp b/_others/others_test_cpp.cpp
index ea880fe..e98f371 100644
--- a/_others/others_test_cpp.cpp
+++ b/_others/others_test_cpp.cpp
@@ -11,7 +11,7 @@ struct Attendee {
 
 
 int get_max_attendees_amount(std::vector<Attendee> attendees_schedule) {
-    std::array<int, MAX_T> bucket{};
+    std::array<int, MAX_T> bucket {};
     for (const auto [enter_time, exit_time] : attendees_schedule) {
         for (int t = enter_time; t < exit_time; t++) {
             bucket[t]++;
@@ -43,6 +43,12 @@ int main() {
 
     std::cout << attendees.size() << ' ' << get_max_attendees_amount(attendees) << std::endl;
 
+    int x = 6, ans = 0;
+    if (x > 5)
+        if (x > 10) ans = 1;
+        else
+            ans = 2;
+    std::cout << ans;
 
     return 0;
 }
diff --git a/cs101/2023mid/exam_2023mid_05_mask.cpp b/cs101/2023mid/exam_2023mid_05_mask.cpp
new file mode 100644
index 0000000..c39b027
--- /dev/null
+++ b/cs101/2023mid/exam_2023mid_05_mask.cpp
@@ -0,0 +1,18 @@
+#include <iostream>
+#include <vector>
+
+using GridRow = std::vector<int>;
+using Grid = std::pmr::vector<GridRow>;
+
+int n;
+std::vector<std::vector<bool>> infected, wearing_mask;
+std::vector<std::vector<int>> infection_flag;
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    std::cin >> n;
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_12_04_day_delta.cpp b/cs101/stage_2/dh_12_04_date_delta.cpp
similarity index 98%
rename from cs101/stage_2/dh_12_04_day_delta.cpp
rename to cs101/stage_2/dh_12_04_date_delta.cpp
index 8cd8096..b6f3050 100644
--- a/cs101/stage_2/dh_12_04_day_delta.cpp
+++ b/cs101/stage_2/dh_12_04_date_delta.cpp
@@ -1,5 +1,4 @@
 #include <iostream>
-#include <math.h>
 
 constexpr int DAYS_OF_MONTHS[13] = {-1, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
 
diff --git a/cs101/stage_2/dh_14_01_day_of_date.cpp b/cs101/stage_2/dh_14_01_day_of_date.cpp
new file mode 100644
index 0000000..de314ff
--- /dev/null
+++ b/cs101/stage_2/dh_14_01_day_of_date.cpp
@@ -0,0 +1,98 @@
+#include <iostream>
+#include <sstream>
+#include <unordered_map>
+
+constexpr int DAYS_OF_MONTHS[13] = {-1, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
+const std::unordered_map<std::string, int> MONTHS_DICT = {
+    {"Jan", 1},
+    {"Feb", 2},
+    {"Mar", 3},
+    {"Apr", 4},
+    {"May", 5},
+    {"Jun", 6},
+    {"Jul", 7},
+    {"Aug", 8},
+    {"Sep", 9},
+    {"Oct", 10},
+    {"Nov", 11},
+    {"Dec", 12},
+};
+const std::unordered_map<int, std::string> DAYS_ENG = {
+    {1, "Mon"},
+    {2, "Tue"},
+    {3, "Wed"},
+    {4, "Thu"},
+    {5, "Fri"},
+    {6, "Sat"},
+    {7, "Sun"},
+};
+
+constexpr bool is_leap(int year) {
+    return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);
+}
+
+constexpr int get_days_of_month(int year, int month) {
+    if (month == 2) { return is_leap(year) ? 29 : 28; }
+    return DAYS_OF_MONTHS[month];
+}
+
+constexpr int get_days_of_year(int year) {
+    return is_leap(year) ? 366 : 365;
+}
+
+constexpr int calc_passed_days(int year, int month, int day) {
+    int passed_days = 0;
+    for (int m = 1; m < month; m++) {
+        passed_days += get_days_of_month(year, m);
+    }
+    return passed_days + day;
+}
+
+constexpr int calc_remaining_days(int year, int month, int day) {
+    return get_days_of_year(year) - calc_passed_days(year, month, day);
+}
+
+constexpr int calc_days_delta(int year1, int month1, int day1,
+                              int year2, int month2, int day2) {
+    int days_delta = 0;
+    if (year1 == year2) {
+        return calc_passed_days(year2, month2, day2) - calc_passed_days(year1, month1, day1);
+    }
+    for (int y = year1 + 1; y < year2; y++) {
+        days_delta += get_days_of_year(y);
+    }
+    return days_delta
+        + calc_remaining_days(year1, month1, day1)
+        + calc_passed_days(year2, month2, day2);
+}
+
+std::tuple<int, int, int> parse_date(std::string s) {
+    std::istringstream ss(s);
+    std::string token;
+    int y, m, d;
+    while (std::getline(ss, token, '-')) {
+        if (token.size() == 4) {
+            y = std::stoi(token);
+        } else if (token.size() == 2) {
+            d = std::stoi(token);
+        } else {
+            m = MONTHS_DICT.at(token);
+        }
+    }
+    return std::make_tuple(y, m, d);
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    std::string date_string;
+    std::cin >> date_string;
+    while (std::cin >> date_string) {
+        auto [y, m, d] = parse_date(date_string);
+        int delta = calc_days_delta(1900, 1, 1, y, m, d);
+        std::cout << DAYS_ENG.at(delta % 7 + 1) << '.' << std::endl;
+    }
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_14_02_special_location.cpp b/cs101/stage_2/dh_14_02_special_location.cpp
new file mode 100644
index 0000000..31bcb03
--- /dev/null
+++ b/cs101/stage_2/dh_14_02_special_location.cpp
@@ -0,0 +1,48 @@
+#include <algorithm>
+#include <array>
+#include <iostream>
+
+constexpr std::size_t GRID_SIZE = 5;
+
+std::array<std::array<int, GRID_SIZE>, GRID_SIZE> grid;
+std::array<int, GRID_SIZE> row_max;
+std::array<int, GRID_SIZE> col_min;
+
+void init_maxs() {
+    for (int i = 0; i < GRID_SIZE; i++) {
+        row_max[i] = *std::max_element(grid[i].begin(), grid[i].end());
+    }
+    for (int j = 0; j < GRID_SIZE; j++) {
+        col_min[j] = grid[0][j];
+        for (int i = 1; i < GRID_SIZE; i++) {
+            col_min[j] = std::min(col_min[j], grid[i][j]);
+        }
+    }
+}
+
+void print_ans() {
+    for (int i = 0; i < GRID_SIZE; i++) {
+        for (int j = 0; j < GRID_SIZE; j++) {
+            if (grid[i][j] == row_max[i] && grid[i][j] == col_min[j]) {
+                std::cout << i + 1 << " " << j + 1 << " " << grid[i][j] << std::endl;
+                return;
+            }
+        }
+    }
+    std::cout << "not found" << std::endl;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    for (int i = 0; i < GRID_SIZE; i++) {
+        for (int j = 0; j < GRID_SIZE; j++) {
+            std::cin >> grid[i][j];
+        }
+    }
+    init_maxs();
+    print_ans();
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_14_03_linear_equations.cpp b/cs101/stage_2/dh_14_03_linear_equations.cpp
new file mode 100644
index 0000000..351bb71
--- /dev/null
+++ b/cs101/stage_2/dh_14_03_linear_equations.cpp
@@ -0,0 +1,69 @@
+#include <algorithm>
+#include <array>
+#include <iostream>
+
+using RopeData = std::pair<int, int>;
+
+constexpr std::size_t N = 5;
+int max_height;
+std::array<RopeData, N> rope_counts{};
+
+
+void print_solution() {
+    std::array<RopeData, N> rope_lengths{};
+    for (int i = 0; i < N; i++) {
+        rope_lengths[i].first = rope_counts[i].first;
+    }
+    for (int height = 1; height <= max_height; height++) {
+        for (rope_lengths[0].second = 0;
+             rope_lengths[0].second < height / rope_counts[0].second;
+             rope_lengths[0].second++) {
+            if (height == 721 && rope_lengths[0].second == 265) {
+                std::clog << height << ' ' << rope_lengths[0].second << std::endl;
+            }
+
+            bool is_valid = true;
+            for (int i = 1; i < N; i++) {
+                rope_lengths[i].second = height - rope_lengths[i - 1].second * rope_counts[i - 1].second;
+                if (rope_lengths[i].second <= 0 || rope_lengths[i].second == rope_lengths[i - 1].second) {
+                    is_valid = false;
+                    break;
+                }
+            }
+
+            if (height - rope_lengths[N - 1].second * rope_counts[N - 1].second != rope_lengths[0].second) {
+                is_valid = false;
+            }
+            if (is_valid) {
+                // std::sort(rope_lengths.begin(), rope_lengths.end(), std::greater<>());
+                std::cout << height;
+                for (const auto& rope : rope_lengths) {
+                    std::cout << ' ' << rope.second;
+                }
+                std::cout << std::endl;
+                return;
+            }
+        }
+    }
+    std::cout << "not found" << std::endl;
+}
+
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    std::cin >> max_height;
+    max_height *= 100;
+
+    for (int i = 0; i < N; i++) {
+        rope_counts[i].first = i;
+        std::cin >> rope_counts[i].second;
+    }
+
+    // std::sort(rope_counts.begin(), rope_counts.end(), std::greater<>());
+    print_solution();
+
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_14_03_linear_equations_COMPLICATED.cpp b/cs101/stage_2/dh_14_03_linear_equations_COMPLICATED.cpp
new file mode 100644
index 0000000..8759289
--- /dev/null
+++ b/cs101/stage_2/dh_14_03_linear_equations_COMPLICATED.cpp
@@ -0,0 +1,63 @@
+#include <array>
+#include <iostream>
+
+constexpr std::size_t ORDER = 5;
+
+std::array<std::array<int, ORDER>, ORDER> matrix;
+
+std::ostream& operator<<(std::ostream& os, const std::array<int, ORDER>& row) {
+    for (int i = 0; i < ORDER; i++) {
+        os << row[i] << " ";
+    }
+    os << std::endl;
+    return os;
+}
+
+std::ostream& operator<<(std::ostream& os, const std::array<std::array<int, ORDER>, ORDER>& matrix) {
+    for (const auto& row : matrix) {
+        os << row;
+    }
+    return os;
+}
+
+void simplify_matrix() {
+    for (int i = 1; i < ORDER; i++) {
+        for (int j = i; j < ORDER; j++) {
+            if (matrix[j][i - 1] != 0) {
+                int temp = matrix[j][i - 1];
+                for (int k = 0; k < ORDER; k++) {
+                    matrix[j][k] = matrix[j][k] * matrix[i - 1][i - 1] - matrix[i - 1][k] * temp;
+                }
+            }
+            std::clog << matrix << std::endl;
+        }
+    }
+}
+
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    int max_height;
+    std::array<int, ORDER> values{};
+    std::cin >> max_height;
+    max_height *= 100;
+
+    for (int i = 0; i < ORDER; i++) {
+        std::cin >> values[i];
+    }
+    for (int i = 0; i < ORDER; i++) {
+        matrix[i][i] = values[i];
+        matrix[i][(i + 1) % ORDER] = 1 - values[(i + 1) % ORDER];
+        matrix[i][(i + 2) % ORDER] = -1;
+    }
+    std::clog << matrix << std::endl;
+
+    simplify_matrix();
+
+    std::clog << matrix << std::endl;
+
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_14_04_eat.cpp b/cs101/stage_2/dh_14_04_eat.cpp
new file mode 100644
index 0000000..1fc031d
--- /dev/null
+++ b/cs101/stage_2/dh_14_04_eat.cpp
@@ -0,0 +1,26 @@
+#include <array>
+#include <iostream>
+
+using Person = char;
+using Order = std::string;
+
+bool judge(Order order, Person a, Person b) {
+    return order.find(a) < order.find(b);
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    for (auto order : {"ABC", "ACB", "BAC", "BCA", "CAB", "CBA"}) {
+        std::array<int, 3> judges{};
+        judges[0] = judge(order, 'A', 'B');
+        judges[1] = judge(order, 'B', 'A') + judge(order, 'C', 'A');
+        judges[2] = judge(order, 'B', 'C') + judge(order, 'A', 'B');
+        if (judges[order[0] - 'A'] > judges[order[1] - 'A'] &&
+            judges[order[1] - 'A'] > judges[order[2] - 'A']) {
+            std::cout << order << std::endl;
+        }
+    }
+    return 0;
+}
diff --git a/cs101/stage_2/dh_14_05_flip_words.cpp b/cs101/stage_2/dh_14_05_flip_words.cpp
new file mode 100644
index 0000000..911a27a
--- /dev/null
+++ b/cs101/stage_2/dh_14_05_flip_words.cpp
@@ -0,0 +1,23 @@
+#include <iostream>
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    std::string line;
+    std::getline(std::cin, line);
+    line += ' ';
+
+    for (int i = 0; i < line.size(); i++) {
+        if (line[i] == ' ') {
+            for (int j = i - 1; j >= 0 && line[j] != ' '; j--) {
+                std::cout << line[j];
+            }
+            if (i != line.size() - 1) {
+                std::cout << line[i];
+            }
+        }
+    }
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_14_06_number_systems.cpp b/cs101/stage_2/dh_14_06_number_systems.cpp
new file mode 100644
index 0000000..9890e51
--- /dev/null
+++ b/cs101/stage_2/dh_14_06_number_systems.cpp
@@ -0,0 +1,60 @@
+#include <algorithm>
+#include <iostream>
+
+using BasedNumber = std::string;
+
+constexpr short char_to_digit(const char c) {
+    if (c >= '0' && c <= '9') {
+        return c - '0';
+    }
+    if (c >= 'a' && c <= 'f') {
+        return c - 'a' + 10;
+    }
+    return -1;
+}
+
+constexpr char digit_to_char(const short d) {
+    if (d >= 0 && d <= 9) {
+        return static_cast<char>('0' + d);
+    }
+    if (d >= 10 && d <= 15) {
+        return static_cast<char>('a' + d - 10);
+    }
+    return '?';
+}
+
+unsigned long long based_to_dec(BasedNumber based_number, unsigned short base) {
+    unsigned long long dec = 0;
+    for (int i = 0; i < based_number.size(); i++) {
+        dec *= base;
+        dec += char_to_digit(based_number[i]);
+    }
+    return dec;
+}
+
+BasedNumber dec_to_based(unsigned long long dec, unsigned short base) {
+    BasedNumber based_number;
+    while (dec > 0) {
+        based_number.push_back(digit_to_char(dec % base));
+        dec /= base;
+    }
+    std::reverse(based_number.begin(), based_number.end());
+    return based_number;
+}
+
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+    std::string num1, num2;
+    unsigned short base1, base2, base3;
+    std::cin >> base1 >> num1 >> base2 >> num2 >> base3;
+
+    unsigned long long dec1 = based_to_dec(num1, base1);
+    unsigned long long dec2 = based_to_dec(num2, base2);
+    unsigned long long dec3 = dec1 + dec2;
+    std::clog << dec1 << " " << dec2 << " " << dec3 << std::endl;
+    std::cout << dec_to_based(dec3, base3) << std::endl;
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_15_01_is_abbr.cpp b/cs101/stage_2/dh_15_01_is_abbr.cpp
new file mode 100644
index 0000000..822e3e2
--- /dev/null
+++ b/cs101/stage_2/dh_15_01_is_abbr.cpp
@@ -0,0 +1,32 @@
+#include <iostream>
+#include <sstream>
+
+bool is_abbr(std::string target, std::string original) {
+    if (target.size() >= original.size()) { return false; }
+    int i = 0, j = 0;
+    for (; i < target.size() && j < original.size(); j++) {
+        if (target[i] == original[j]) { i++; }
+    }
+    if (i == target.size()) { return true; }
+    return false;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    std::string temp;
+    std::getline(std::cin, temp);
+    int n = std::stoi(temp);
+
+    for (int _ = 0; _ < n; _++) {
+        std::string target, original;
+        std::getline(std::cin, temp);
+        std::istringstream ss(temp);
+        std::getline(ss, target, ':');
+        std::getline(ss, original);
+        std::cout << (is_abbr(target, original) ? "YES" : "NO") << std::endl;
+    }
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_15_02_tiny_kmp.cpp b/cs101/stage_2/dh_15_02_tiny_kmp.cpp
new file mode 100644
index 0000000..60160c6
--- /dev/null
+++ b/cs101/stage_2/dh_15_02_tiny_kmp.cpp
@@ -0,0 +1,55 @@
+#include <iostream>
+#include <sstream>
+#include <vector>
+
+std::vector<int> prefix_function(const std::string& s) {
+    std::vector<int> pi(s.size());
+    for (int i = 1; i < s.size(); i++) {
+        int j = pi[i - 1];
+        while (j > 0 && s[i] != s[j]) {
+            j = pi[j - 1];
+        }
+        if (s[i] == s[j]) { j++; }
+        pi[i] = j;
+    }
+    return pi;
+}
+
+std::vector<int> find_substr_pos(const std::string& s, const std::string& subs) {
+    std::string concat_string = subs + '\0' + s;
+    auto pi = prefix_function(concat_string);
+    std::vector<int> positions;
+    for (int i = subs.size(); i < concat_string.size(); i++) {
+        if (pi[i] == subs.size()) { positions.push_back(i - 2 * subs.size()); }
+    }
+    return positions;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    std::string line;
+    std::string s, subs1, subs2;
+
+    while (std::getline(std::cin, line)) {
+        std::istringstream iss(line);
+        std::getline(iss, s, ',');
+        std::getline(iss, subs1, ',');
+        std::getline(iss, subs2, ',');
+        auto subs1_pos = find_substr_pos(s, subs1), subs2_pos = find_substr_pos(s, subs2);
+        if (subs1.empty() || subs2.empty()) {
+            std::cout << -1 << std::endl;
+            continue;
+        }
+        auto start_pos = subs1_pos[0] + subs1.size();
+        auto end_pos = subs2_pos[subs2_pos.size() - 1];
+        if (start_pos > end_pos) {
+            std::cout << -1 << std::endl;
+        } else {
+            std::cout << end_pos - start_pos << std::endl;
+        }
+    }
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_15_03_courage_machine.cpp b/cs101/stage_2/dh_15_03_courage_machine.cpp
new file mode 100644
index 0000000..e26c00c
--- /dev/null
+++ b/cs101/stage_2/dh_15_03_courage_machine.cpp
@@ -0,0 +1,28 @@
+#include <algorithm>
+#include <iostream>
+
+std::string calc_sequence(int n) {
+    std::string sequence;
+    while (n) {
+        if (n % 2) {
+            sequence += 'N';
+            n = (n - 1) / 2;
+        } else {
+            sequence += 'G';
+            n = (n - 2) / 2;
+        }
+    }
+    std::reverse(sequence.begin(), sequence.end());
+    return sequence;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    int n;
+    std::cin >> n;
+    std::cout << calc_sequence(n) << std::endl;
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_15_04_related_months.cpp b/cs101/stage_2/dh_15_04_related_months.cpp
new file mode 100644
index 0000000..d2aaaac
--- /dev/null
+++ b/cs101/stage_2/dh_15_04_related_months.cpp
@@ -0,0 +1,49 @@
+#include <iostream>
+
+constexpr bool is_leap(int year) {
+    if (year % 40000 == 0) { return false; }
+    if (year % 10000 == 0) { return false; }
+    if (year % 400 == 0) { return true; }
+    if (year % 100 == 0) { return false; }
+    return year % 4 == 0;
+}
+
+constexpr int get_days_in_month(int year, int month) {
+    switch (month) {
+    case 1: return 31;
+    case 2: return is_leap(year) ? 29 : 28;
+    case 3: return 31;
+    case 4: return 30;
+    case 5: return 31;
+    case 6: return 30;
+    case 7: return 31;
+    case 8: return 31;
+    case 9: return 30;
+    case 10: return 31;
+    case 11: return 30;
+    case 12: return 31;
+    default: throw std::invalid_argument("Invalid month");
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    int n;
+    std::cin >> n;
+    for (int _ = 0; _ < n; _++) {
+        int year, month1, month2;
+        std::cin >> year >> month1 >> month2;
+        if (month1 > month2) {
+            std::swap(month1, month2);
+        }
+        int days = 0;
+        for (int m = month1; m < month2; m++) {
+            days += get_days_in_month(year, m);
+        }
+        std::cout << (days % 7 == 0 ? "YES" : "NO") << std::endl;
+    }
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_15_05_clinic_queue.cpp b/cs101/stage_2/dh_15_05_clinic_queue.cpp
new file mode 100644
index 0000000..9fae2da
--- /dev/null
+++ b/cs101/stage_2/dh_15_05_clinic_queue.cpp
@@ -0,0 +1,48 @@
+#include <algorithm>
+#include <iomanip>
+#include <iostream>
+#include <numeric>
+#include <vector>
+
+template <typename T>
+struct ElemWithIndex {
+    T value;
+    std::size_t idx;
+    bool operator<(ElemWithIndex other) const { return value < other.value; }
+    auto operator+(ElemWithIndex other) -> decltype(value + value) { return value + other.value; }
+};
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    int n;
+    std::cin >> n;
+
+    std::vector<ElemWithIndex<int>> times(n);
+    for (int i = 0; i < n; ++i) {
+        times[i].idx = i + 1;
+        std::cin >> times[i].value;
+    }
+    std::stable_sort(times.begin(), times.end());
+
+    bool first = true;
+    for (auto& [_, idx] : times) {
+        if (!first) { std::cout << " "; }
+        std::cout << idx;
+        first = false;
+    }
+
+    std::vector<int> wait_times(times.size());
+
+    for (int i = 1; i < times.size(); i++) {
+        wait_times[i] = wait_times[i - 1] + times[i - 1].value;
+    }
+
+    int sum = std::accumulate(wait_times.begin(), wait_times.end(), 0);
+
+    std::cout << std::endl << std::fixed << std::setprecision(2) << 1.0 * sum / times.size() << std::endl;
+
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_15_06_pass_balls.cpp b/cs101/stage_2/dh_15_06_pass_balls.cpp
new file mode 100644
index 0000000..f9baced
--- /dev/null
+++ b/cs101/stage_2/dh_15_06_pass_balls.cpp
@@ -0,0 +1,20 @@
+#include <iostream>
+#include <numeric>
+
+int calc_max_ans(int n) {
+    for (int i = n / 2; i >= 1; i--) {
+        if (std::gcd(i, n) == 1) { return i; }
+    }
+    __builtin_unreachable();
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    int n;
+    std::cin >> n;
+    std::cout << calc_max_ans(n) << std::endl;
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_15_07_char_stat.cpp b/cs101/stage_2/dh_15_07_char_stat.cpp
new file mode 100644
index 0000000..5d0bc5b
--- /dev/null
+++ b/cs101/stage_2/dh_15_07_char_stat.cpp
@@ -0,0 +1,35 @@
+#include <algorithm>
+#include <iostream>
+#include <map>
+
+void print_char_map(std::map<char, int> map, std::ostream& os) {
+    int max_num = std::max_element(map.begin(), map.end(),
+                                   [](auto a, auto b) { return a.second < b.second; })->second;
+    for (; max_num > 0; max_num--) {
+        std::string line = "#";
+        for (char c : "ABCDEFGHIJKLMNOPQRSTUVWXYZ") {
+            if (map[c] >= max_num) {
+                line += " *";
+            } else {
+                line += "  ";
+            }
+        }
+        while (!line.empty() && line.back() == ' ') { line.pop_back(); }
+        std::cout << line << std::endl;
+    }
+    std::cout << "# A B C D E F G H I J K L M N O P Q R S T U V W X Y Z" << std::endl;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    std::map<char, int> char_map;
+    std::string line;
+    while (std::cin >> line) {
+        for (auto c : line) { char_map[c]++; }
+    }
+    print_char_map(char_map, std::cout);
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_15_08_matrix_modification.cpp b/cs101/stage_2/dh_15_08_matrix_modification.cpp
new file mode 100644
index 0000000..197c250
--- /dev/null
+++ b/cs101/stage_2/dh_15_08_matrix_modification.cpp
@@ -0,0 +1,80 @@
+#include <iostream>
+#include <vector>
+
+using CharMatrix = std::vector<std::vector<char>>;
+
+bool operator==(const CharMatrix& a, const CharMatrix& b) {
+    for (int i = 0; i < a.size(); i++) {
+        for (int j = 0; j < a.size(); j++) {
+            if (a[i][j] != b[i][j]) { return false; }
+        }
+    }
+    return true;
+}
+
+CharMatrix get_init_matrix(std::size_t n, char value = 0) {
+    return std::vector(n, std::vector<char>(n, value));
+}
+
+CharMatrix rotated_clockwise(const CharMatrix& matrix) {
+    CharMatrix new_matrix = get_init_matrix(matrix.size());
+    for (int i = 0; i < matrix.size(); i++) {
+        for (int j = 0; j < matrix.size(); j++) {
+            new_matrix[j][matrix.size() - i - 1] = matrix[i][j];
+        }
+    }
+    return new_matrix;
+}
+
+CharMatrix rotated_counterclockwise(const CharMatrix& matrix) {
+    CharMatrix new_matrix = get_init_matrix(matrix.size());
+    for (int i = 0; i < matrix.size(); i++) {
+        for (int j = 0; j < matrix.size(); j++) {
+            new_matrix[i][j] = matrix[j][matrix.size() - i - 1];
+        }
+    }
+    return new_matrix;
+}
+
+CharMatrix central_symmetry_transformed(const CharMatrix& matrix) {
+    CharMatrix new_matrix = get_init_matrix(matrix.size());
+    for (int i = 0; i < matrix.size(); i++) {
+        for (int j = 0; j < matrix.size(); j++) {
+            new_matrix[matrix.size() - i - 1][matrix.size() - j - 1] = matrix[i][j];
+        }
+    }
+    return new_matrix;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    int n;
+    std::cin >> n;
+    CharMatrix old_matrix = get_init_matrix(n), new_matrix = get_init_matrix(n);
+    for (int i = 0; i < n; i++) {
+        for (int j = 0; j < n; j++) {
+            std::cin >> old_matrix[i][j];
+        }
+    }
+    for (int i = 0; i < n; i++) {
+        for (int j = 0; j < n; j++) {
+            std::cin >> new_matrix[i][j];
+        }
+    }
+
+    if (new_matrix == old_matrix) {
+        std::cout << 4 << std::endl;
+    } else if (rotated_clockwise(old_matrix) == new_matrix) {
+        std::cout << 1 << std::endl;
+    } else if (rotated_counterclockwise(old_matrix) == new_matrix) {
+        std::cout << 2 << std::endl;
+    } else if (central_symmetry_transformed(old_matrix) == new_matrix) {
+        std::cout << 3 << std::endl;
+    } else {
+        std::cout << 5 << std::endl;
+    }
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_16_01_shit_pair_nums.cpp b/cs101/stage_2/dh_16_01_shit_pair_nums.cpp
new file mode 100644
index 0000000..b12050b
--- /dev/null
+++ b/cs101/stage_2/dh_16_01_shit_pair_nums.cpp
@@ -0,0 +1,54 @@
+#include <iostream>
+#include <vector>
+
+std::vector<int> primes;
+std::vector<bool> is_not_prime;
+
+void prime_sieve(int max_n) {
+    is_not_prime.resize(max_n + 1);
+    for (int i = 2; i * i <= max_n; i++) {
+        if (!is_not_prime[i])
+            for (int j = i + i; j <= max_n; j += i) {
+                is_not_prime[j] = true;
+            }
+    }
+    for (int i = 2; i <= max_n; i++) {
+        if (!is_not_prime[i]) {
+            primes.push_back(i);
+        }
+    }
+}
+
+std::vector<int> get_prime_factors(int x) {
+    std::vector<int> prime_factors;
+    for (int prime : primes) {
+        if (x % prime == 0) {
+            prime_factors.push_back(prime);
+            while (x && x % prime == 0) { x /= prime; }
+        }
+        if (!x) { break; }
+    }
+    return prime_factors;
+}
+
+bool operator==(std::vector<int> a, std::vector<int> b) {
+    if (a.size() != b.size()) { return false; }
+    for (int i = 0; i < a.size(); i++) {
+        if (a[i] != b[i]) { return false; }
+    }
+    return true;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    int x, y;
+    char temp_comma;
+    std::cin >> x >> temp_comma >> y;
+    prime_sieve(std::max(x, y));
+
+    std::cout << (get_prime_factors(x) == get_prime_factors(y) ? "YES" : "NO") << std::endl;
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_16_02.cpp b/cs101/stage_2/dh_16_02.cpp
new file mode 100644
index 0000000..01248b6
--- /dev/null
+++ b/cs101/stage_2/dh_16_02.cpp
@@ -0,0 +1,17 @@
+#include <algorithm>
+#include <iostream>
+#include <vector>
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    int n;
+    std::cin >> n;
+    std::vector<int> patients(n);
+    for (int i = 0; i < n; i++) { std::cin >> patients[i]; }
+
+    std::cout << (std::min_element(patients.begin(), patients.end()) - patients.begin()) << std::endl;
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_16_03_arrange_activities.cpp b/cs101/stage_2/dh_16_03_arrange_activities.cpp
new file mode 100644
index 0000000..84de401
--- /dev/null
+++ b/cs101/stage_2/dh_16_03_arrange_activities.cpp
@@ -0,0 +1,32 @@
+#include <algorithm>
+#include <iostream>
+#include <vector>
+
+using Range = std::pair<int, int>;
+constexpr int INF = 0x3f3f3f3f;
+
+int calc_ans(std::vector<Range> time_ranges) {
+    std::sort(time_ranges.begin(), time_ranges.end(),
+              [](auto a, auto b) { return a.second < b.second; });
+    int i = 0, current_timestamp = -INF, ans = 0;
+    while (i < time_ranges.size()) {
+        current_timestamp = time_ranges[i].second;
+        ans++;
+        while (i < time_ranges.size() && time_ranges[i].first < current_timestamp) { i++; }
+    }
+    return ans;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    int n;
+    std::cin >> n;
+    std::vector<Range> time_ranges(n);
+    for (int i = 0; i < n; i++) { std::cin >> time_ranges[i].first >> time_ranges[i].second; }
+    std::cout << calc_ans(time_ranges) << std::endl;
+
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_16_06_line_wrap.cpp b/cs101/stage_2/dh_16_06_line_wrap.cpp
new file mode 100644
index 0000000..8c6c231
--- /dev/null
+++ b/cs101/stage_2/dh_16_06_line_wrap.cpp
@@ -0,0 +1,31 @@
+#include <iostream>
+#include <vector>
+
+using ParagraphSeparated = std::vector<std::string>;
+
+void print_paragraph(const ParagraphSeparated& paragraph, int wrap_pos = 80, std::ostream& os = std::cout) {
+    int line_length = 0;
+    for (const auto& word : paragraph) {
+        if (line_length + word.size() > wrap_pos) {
+            os << std::endl;
+            line_length = 0;
+        }
+        if (line_length != 0) { os << ' '; }
+        os << word;
+        line_length += word.size() + 1;
+    }
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    int word_count;
+    std::cin >> word_count;
+
+    ParagraphSeparated paragraph(word_count);
+    for (int i = 0; i < word_count; i++) { std::cin >> paragraph[i]; }
+    print_paragraph(paragraph);
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_16_07_observer_stone.cpp b/cs101/stage_2/dh_16_07_observer_stone.cpp
new file mode 100644
index 0000000..06c19da
--- /dev/null
+++ b/cs101/stage_2/dh_16_07_observer_stone.cpp
@@ -0,0 +1,40 @@
+#include <algorithm>
+#include <iostream>
+#include <vector>
+
+bool run() {
+    int n, radius;
+    std::cin >> radius >> n;
+    if (radius == -1) { return false; }
+    std::vector<int> pos(n);
+    for (int i = 0; i < n; i++) { std::cin >> pos[i]; }
+    std::sort(pos.begin(), pos.end());
+
+    int uncovered_idx = 0, observer_idx = -1, observer_count = 0;
+    while (uncovered_idx < n) {
+        // 找下一个雷达
+        for (observer_idx = uncovered_idx;
+             observer_idx < n && pos[observer_idx] - pos[uncovered_idx] <= radius;
+             observer_idx++) {}
+        observer_idx--;
+        std::clog << '[' << observer_idx << ']' << pos[observer_idx] << " ";
+        observer_count++;
+        // 找下一个盖不住的兵
+        for (uncovered_idx = observer_idx;
+             uncovered_idx < n && pos[uncovered_idx] - pos[observer_idx] <= radius;
+             uncovered_idx++) {}
+    }
+    std::clog << std::endl;
+
+    std::cout << observer_count << std::endl;
+    return true;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    while (run()) {}
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_16_08_tianji_horse.cpp b/cs101/stage_2/dh_16_08_tianji_horse.cpp
new file mode 100644
index 0000000..0bcf4a9
--- /dev/null
+++ b/cs101/stage_2/dh_16_08_tianji_horse.cpp
@@ -0,0 +1,55 @@
+#include <algorithm>
+#include <iostream>
+#include <vector>
+
+int calc_wins(std::vector<int> king_times, std::vector<int> tianji_times) {
+    std::sort(king_times.begin(), king_times.end());
+    std::sort(tianji_times.begin(), tianji_times.end());
+    int wins = 0, k = -1;
+    std::vector<bool> king_used(king_times.size()), tianji_used(tianji_times.size());
+    // 先用最邻近的马战胜齐王，O(n^2)
+    for (int i = 0; i < king_times.size(); i++) {
+        do { k++; } while (k < tianji_times.size() && tianji_times[k] < king_times[i]);
+        do { k--; } while (k >= 0 && tianji_used[k]);
+        if (k >= 0) {
+            king_used[i] = true, tianji_used[k] = true;
+            wins++;
+            std::clog << '[' << i << '<' << k << "] ";
+        }
+    }
+    std::clog << std::endl;
+    // 没有赢的资本了，尽量平局
+    for (int i = 0; i < king_times.size(); i++) {
+        if (king_used[i]) { continue; }
+        for (int j = 0; j < tianji_times.size(); j++) {
+            if (tianji_used[j]) { continue; }
+            if (king_times[i] == tianji_times[j]) {
+                // ties++;
+                king_used[i] = true, tianji_used[j] = true;
+                std::clog << '(' << i << ',' << j << ") ";
+                break;
+            }
+        }
+    }
+    std::clog << std::endl;
+    // 只剩下输的资本了
+    int loses = static_cast<int>(std::count(king_used.begin(), king_used.end(), false));
+    std::clog << "LOSES " << loses << std::endl;
+
+    return wins - loses;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    int n;
+    while (std::cin >> n && n) {
+        std::vector<int> king_times(n), tianji_times(n);
+        for (int i = 0; i < n; i++) { std::cin >> king_times[i]; }
+        for (int i = 0; i < n; i++) { std::cin >> tianji_times[i]; }
+        std::cout << 200 * calc_wins(king_times, tianji_times) << std::endl;
+    }
+
+    return 0;
+}
diff --git a/cs101/stage_2/dh_16_08_tianji_horse_WRONG.cpp b/cs101/stage_2/dh_16_08_tianji_horse_WRONG.cpp
new file mode 100644
index 0000000..3ab470f
--- /dev/null
+++ b/cs101/stage_2/dh_16_08_tianji_horse_WRONG.cpp
@@ -0,0 +1,35 @@
+#include <algorithm>
+#include <iostream>
+#include <vector>
+
+int calc_wins(std::vector<int> king_times, std::vector<int> tianji_times) {
+    std::sort(king_times.begin(), king_times.end());
+    std::sort(tianji_times.begin(), tianji_times.end());
+    int wins = 0, i = 0, j = 0, ties = 0;
+    while (i < king_times.size()) {
+        if (king_times[i] < tianji_times[j]) {
+            wins--, i++;
+        } else if (king_times[i] > tianji_times[j]) {
+            wins++, i++, j++;
+        } else {
+            ties++, i++, j++;
+        }
+    }
+    if (ties < 2) {ties = 2;}
+    return wins + ties - 2;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    int n;
+    while (std::cin >> n && n) {
+        std::vector<int> king_times(n), tianji_times(n);
+        for (int i = 0; i < n; i++) { std::cin >> king_times[i]; }
+        for (int i = 0; i < n; i++) { std::cin >> tianji_times[i]; }
+        std::cout << 200 * calc_wins(king_times, tianji_times) << std::endl;
+    }
+
+    return 0;
+}
diff --git a/dsa/ch5_binary_tree/dsa_0514_heap.cpp b/dsa/ch5_binary_tree/dsa_0514_heap.cpp
new file mode 100644
index 0000000..9f5017f
--- /dev/null
+++ b/dsa/ch5_binary_tree/dsa_0514_heap.cpp
@@ -0,0 +1,41 @@
+#include <functional>
+#include <iostream>
+#include <queue>
+
+template <typename T, std::function<bool(T, T)>>
+class Heap {
+public:
+    class Node {
+        T value;
+        Node *father = nullptr, *left = nullptr, *right = nullptr;
+    };
+
+    Node* root = nullptr;
+
+    Node* push(T value) {
+        if (root == nullptr) { return root = new Node(value); }
+        Node* node = root;
+        while (node->right != nullptr) { node = node->right; }
+        if (node->left == nullptr) { return node->left = new Node({.value = value, .father = node}); }
+        return node->right = new Node({.value = value, .father = node});
+    }
+
+    void swap(Node* a, Node* b) {
+        if (a->left != nullptr) { a->left->father = b; }
+        if (a->right != nullptr) { a->right->father = b; }
+        if (b->left != nullptr) { b->left->father = a; }
+        if (b->right != nullptr) { b->right->father = a; }
+        std::swap(a, b);
+    }
+
+    void swim(Node* node) {}
+};
+
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+
+    return 0;
+}
diff --git a/dsa/ch5_binary_tree/dsa_0514_heap_STL.cpp b/dsa/ch5_binary_tree/dsa_0514_heap_STL.cpp
new file mode 100644
index 0000000..589ebf3
--- /dev/null
+++ b/dsa/ch5_binary_tree/dsa_0514_heap_STL.cpp
@@ -0,0 +1,25 @@
+#include <iostream>
+#include<queue>
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    int n, op, u;
+    std::cin >> n;
+    while (std::cin >> n) {
+        std::priority_queue<int, std::vector<int>, std::greater<>> priority_queue;
+        for (int _ = 0; _ < n; _++) {
+            std::cin >> op;
+            if (op == 1) {
+                std::cin >> u;
+                priority_queue.push(u);
+            } else {
+                std::cout << priority_queue.top() << std::endl;
+                priority_queue.pop();
+            }
+        }
+    }
+
+    return 0;
+}