题解 | #【模板】栈#

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

int main(){
    int n;
    string operation;
    vector<int> stack;
    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> operation;
        if (operation == "push") {
            int x;
            cin >> x;
            stack.push_back(x);
        } else if (operation == "pop") {
            if (stack.empty()) {
                cout << "error" << endl;
            } else {
                cout << stack.back() << endl;
                stack.pop_back();
            }
        } else if (operation == "top") {
            if (stack.empty()) {
                cout << "error" << endl;
            } else {
                cout << stack.back() << endl;
            }
        }
    }
    return 0;
}