new algo

Exercise/Homework1/C 队列的实现及基本操作.cpp

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+#include <iostream>
+#include <limits>
+using namespace std;
+
+template <class T>
+class Queue {
+private:
+    T* element;
+    int begin;
+    int end;
+    int capacity;
+
+public:
+    static constexpr T INF = numeric_limits<T>::max();
+
+    Queue(int len) : begin(0), end(0), capacity(len) {
+        element = new T[len];
+    }
+
+    ~Queue() {
+        delete[] element;
+    }
+
+    void push(const T& e) {
+        if (end == capacity) {
+            int newCap = capacity * 2;
+            T* tmp = new T[newCap];
+            for (int i = begin; i < end; i++) {
+                tmp[i - begin] = element[i];
+            }
+            end -= begin;
+            begin = 0;
+            capacity = newCap;
+            delete[] element;
+            element = tmp;
+        }
+        element[end++] = e;
+    }
+
+    void pop() {
+        if (empty()) throw std::invalid_argument("Queue is empty.");
+        begin++;
+    }
+
+    T& front() {
+        if (empty()) throw std::invalid_argument("Queue is empty.");
+        return element[begin];
+    }
+
+    T& back() {
+        if (empty()) throw std::invalid_argument("Queue is empty.");
+        return element[end - 1];
+    }
+
+    bool empty() const {
+        return begin == end;
+    }
+
+    int size() const {
+        return end - begin;
+    }
+};
+
+int main() {
+    int n;
+    cin >> n;
+    Queue<int> q(n);
+
+    for (int i = 0; i < n; i++) {
+        int p;
+        cin >> p;
+        switch (p) {
+            case 0: {
+                if (q.empty()) {
+                    cout << "invalid" << endl;
+                } else {
+                    cout << q.front() << endl;
+                    q.pop();
+                }
+                break;
+            }
+            case 1: {
+                int val;
+                cin >> val;
+                q.push(val);
+                break;
+            }
+            default: {
+                return 0;
+            }
+        }
+    }
+    return 0;
+}