some programs

dp/TJOI2007_walk_segments_dp.cpp

@@ -0,0 +1,64 @@
+#include <iostream>
+
+using namespace std;
+
+using Segment = pair<int, int>;
+
+constexpr int MAX_N = 20005;
+int n;
+Segment segments[MAX_N];
+
+pair<int, int> dp[MAX_N]; // 从这一层的线段左/右边出去
+
+void log_dp() {
+    for (int i = 0; i < n; i++) {
+        clog << dp[i].first << "\t" << dp[i].second << endl;
+    }
+}
+
+pair<int, int> get_min_steps(const Segment& segment, const int start_pos) {
+    const int len = segment.second - segment.first;
+    if (start_pos <= segment.first) {
+        return {segment.second - start_pos + len, segment.second - start_pos};
+    }
+    if (start_pos >= segment.second) {
+        return {start_pos - segment.first, start_pos - segment.first + len};
+    }
+    return {
+        len + (segment.second - start_pos),
+        len + (start_pos - segment.first)
+    };
+}
+
+// pair<int, int> get_min_steps(const Segment& segment, const Segment& previous_segment) {
+//     auto [first1, second1] = get_min_steps(segment, previous_segment.second);
+//     auto [first2, second2] = get_min_steps(segment, previous_segment.first);
+//     return {min(first1, first2), min(second1, second2)};
+// }
+
+int solve_dp() {
+    dp[0] = get_min_steps(segments[0], 1);
+    for (int i = 1; i < n; i++) {
+        auto [first1, second1] = get_min_steps(segments[i], segments[i - 1].first);
+        auto [first2, second2] = get_min_steps(segments[i], segments[i - 1].second);
+        first1 += dp[i - 1].first, second1 += dp[i - 1].first;
+        first2 += dp[i - 1].second, second2 += dp[i - 1].second;
+        dp[i] = {min(first1, first2), min(second1, second2)};
+    }
+    return min(dp[n - 1].first, dp[n - 1].second);
+}
+
+int main() {
+    ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> n;
+    for (int i = 0; i < n; i++) {
+        cin >> segments[i].first >> segments[i].second;
+    }
+    segments[n] = {n, n}, n++;
+    cout << solve_dp() + n - 2 << endl;
+    log_dp();
+
+    return 0;
+}

dp/backpack_dp/NOIP2006S_jinming_budget_dp_knapsack.cpp

@@ -50,7 +50,7 @@ vector<FlatItem> generate_flat_items(OriginalItem item) {
 void solve_dp() {
     for (int i = 0; i < n; i++) {
         if (items[i].item.value == -1) { continue; }
-        for (int w=capacity; w>=1; w--) {
+        for (int w = capacity; w >= 1; w--) {
             // dp[w] = dp[w] // 不买
             for (const auto& [weight, value] : generate_flat_items(items[i])) {
                 if (w >= weight) {