题解 | 【模板】栈

水题，直接用stl的vector模拟stack即可。

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

class stack {
    std::vector<int> a;

public:
    stack() {}
    void push(int x) {
        a.push_back(x);
    }
    void pop() {
        if (a.empty()) {
            std::cout << "error\n";
            return;
        }
        std::cout << a.back() << "\n";
        a.pop_back();
    }
    void top() {
        if (a.empty()) {
            std::cout << "error\n";
            return;
        }
        std::cout << a.back() << "\n";
    }
};

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

    stack stk;
    int n;
    std::cin >> n;

    while (n--) {
        std::string op;
        std::cin >> op;
        if (op == "push") {
            int x;
            std::cin >> x;
            stk.push(x);
        } else if (op == "pop") {
            stk.pop();
        } else {
            stk.top();
        }
    }

    return 0;
}

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