some programs!!

cs101/dh_00_15_jusephus.cpp

@@ -0,0 +1,77 @@
+#include <iostream>
+
+class CycledLinkedList {
+public:
+    struct Node {
+        int val = 0;
+        Node* next = nullptr;
+        Node* prev = nullptr;
+    };
+
+    Node* head = nullptr; // They are POINTERS, not OBJECTS.
+
+    void push_back(int val) {
+        if (head == nullptr) {
+            head = new Node({.val = val});
+            head->next = head;
+            head->prev = head;
+            return;
+        }
+        Node* node = new Node({.val = val});
+        head->prev->next = node;
+        node->prev = head->prev;
+        head->prev = node;
+        node->next = head;
+    }
+
+    void remove(Node* node) {
+        node->prev->next = node->next;
+        node->next->prev = node->prev;
+        if (node == head) {
+            head = node->next;
+        }
+        delete node;
+    }
+
+    void init_cycle(int n) {
+        for (int i = 0; i < n; i++) {
+            push_back(i);
+        }
+    }
+
+    friend std::ostream& operator<<(std::ostream& os, const CycledLinkedList& list) {
+        for (Node* node = list.head->next; node != list.head; node = node->next) {
+            os << node->val << "<->";
+        }
+        os << list.head->val << std::endl;
+        return os;
+    }
+};
+
+int n, m, target_order;
+CycledLinkedList players;
+
+int target_idx() {
+    for (int i = 0; i < target_order - 1; i++) {
+        for (int j = 0; j < m - 1; j++) {
+            players.head = players.head->next;
+        }
+        players.remove(players.head);
+    }
+    for (int j = 0; j < m - 1; j++) {
+        players.head = players.head->next;
+    }
+    return players.head->val;
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    std::cin.tie(nullptr);
+
+    std::cin >> n >> m >> target_order;
+    players.init_cycle(n);
+    // std::clog << players << std::endl;
+    std::cout << target_idx() + 1 << std::endl;
+
+    return 0;
+}