题解 | #【模板】队列#

#include <iostream>
using namespace std;

const int N = 100010;
int a[N];

int main() {
    int n;
    int index = 0;
    int top = 0;
    cin >> n;
    while(n--){
        string s;
        cin >> s;
        if(s == "push"){
            int x;
            cin >> x;
            a[index++] = x;
        }else if(s == "pop"){
            if(index == top) cout << "error" << endl;
            else cout << a[top++] << endl;
        }else if(s == "front"){
            if(index == top) cout << "error" << endl;
            else cout << a[top] << endl;
        }
    }
}
// 64 位输出请用 printf("%lld")

用数组模拟实现，两个指针指向数组，一个为头部，一个为当前元素