题解 | 【模板】队列

水题，开全局数组，双指针维护即可。

#include<bits/stdc++.h>
using i64 = long long;

int q[100010];
int l = 0, r = 0;


int main() {
    std::cin.tie(nullptr)->sync_with_stdio(false);

    int n;
    std::cin >> n;

    while (n--) {
        std::string op;
        std::cin >> op;

        if (op == "push") {
            int x;
            std::cin >> x;
            q[r++] = x;
        } else if (op == "pop") {
            if (l == r) {
                std::cout << "error\n";
            } else {
                std::cout << q[l++] << "\n";
            }
        } else {
            if (l == r) {
                std::cout << "error\n";
            } else {
                std::cout << q[l] << "\n";
            }
        }
    }

    return 0;
}

https://www.nowcoder.com/discuss/727521113110073344