题解 | 【模板】栈的操作

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

class stack {
    private:
        array<int, 100000> arr;
        int len = 0;
    public:
        void push(int x) {
            len++;
            arr[len-1] = x;
        }
        void pop() {
            if (len > 0) {
                len--;
            } else {
                cout << "Empty" << endl;
            }
        }
        void query() {
            if (len > 0) {
                cout << arr[len-1] << endl; 
            } else {
                cout << "Empty" << endl;
            }
        }
        int size() {
            return len;
        }
};


int main() {
    int op;
    cin >> op;
    stack stk;
    while (op--) {
        string s;
        int num;
        cin >> s;
        if (s == "push") {
            cin >> num;
            stk.push(num);
        } else if (s == "pop") {
            stk.pop();
        } else if (s == "query") {
            stk.query();
        } else if (s == "size") {
            cout << stk.size() << endl;
        }

    }


}