题解 | 【模板】队列

C++

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

int main() {
    int n;
    cin >> n;
    int q[100000];
    int idx=-1; // 采取 head rear 更好
    while (n--) {
        string op;
        cin >> op;
        if (op=="push") cin >> q[++idx];
        else if (op=="front" && idx > -1) cout << q[0] << endl;
        else if (op=="pop" && idx > -1) {
            cout << q[0] << endl;
            for (int i=0; i<idx; i++) {
                q[i] = q[i+1];
            }
            idx--;
        }
        else cout << "error" << endl;
    }
    return 0;
}
// 64 位输出请用 printf("%lld")

写成类

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

class queue {
    private:
    int x[100000];
    int head=0, rear=0;
    public:
    int isEmpty() {
        return head==rear;
    }
    void push(int i) {
        x[rear++] = i;
    }
    int pop() {
        return x[head++];
    }
    int front() {
        return x[head];
    }
};

int main() {
    int n;
    cin >> n;
    queue q;
    string op;
    int a;
    while (n--) {
        cin >> op;
        if (op=="push") {
            cin >> a;
            q.push(a);
        }
        else if (op=="front" && !q.isEmpty()) {            
            cout << q.front() << endl;
        }
        else if (op=="pop" && !q.isEmpty()) {
            cout << q.front() << endl;
            q.pop();
        }
        else {
            cout << "error" << endl;
        }
    }
    return 0;
}
// 64 位输出请用 printf("%lld")