每日一题——模拟循环队列

思路：因为要求的循环队列是固定容量的，所以不能使用STL自带的队列来实现。

于是使用vector和两个指针：front和rear，以及一个布尔变量来判满，实现固定容量功能；

#include <iostream>
#include <vector>
using namespace std;

class CircularQueue {
  private:
    vector<int> data;
    int front, rear, maxSize;
    bool fullFlag;

  public:
    CircularQueue(int n) : maxSize(n), front(0), rear(0), fullFlag(false) {
        data.resize(n);
    }

    void push(int x) {
        if (isFull()) {
            cout << "full" << endl;
            return;
        }
        data[rear] = x;
        rear = (rear + 1) % maxSize;
        fullFlag = (rear == front); // 更新队满标志
    }

    void pop() {
        if (isEmpty()) {
            cout << "empty" << endl;
            return;
        }
        cout << data[front] << endl;
        front = (front + 1) % maxSize;
        fullFlag = false;
    }

    void frontElement() {
        if (isEmpty()) {
            cout << "empty" << endl;
            return;
        }
        cout << data[front] << endl;
    }

    bool isEmpty() {
        return (front == rear) && !fullFlag;
    }
    bool isFull() {
        return fullFlag;
    }
};

int main() {
    int n, q;
    cin >> n >> q;
    CircularQueue cq(n);

    string op;
    while (q--) {
        cin >> op;
        if (op == "push") {
            int x;
            cin >> x;
            cq.push(x);
        } else if (op == "pop") {
            cq.pop();
        } else if (op == "front") {
            cq.frontElement();
        }
    }
    return 0;
}