3.模拟栈

 

 

用c++里的stack容器很容易做出来

#include <bits/stdc++.h>
using namespace std;
int main() {
    stack<int> s;
    int n;
    cin >> n;
    while (n--) {
        string op;
        int x;
        cin >> op;
        if (op == "push") {
            cin >> x;
            s.push(x);
        } else if (op == "pop") {
            s.pop();
        } else if (op == "empty") {
            if (s.empty()) {
                cout << "YES" << endl;
            } else {
                cout << "NO" << endl;
            }
        } else if (op == "query") {
            cout << s.top() << endl;
        }
    }
    return 0;
}

现在考察用数组手动实现一个栈

#include <bits/stdc++.h>
using namespace std;
const int N = 100010;
int stk[N], tt;
int main() {
    int m;
    cin >> m;
    while (m--) {
        string s;
        int x;
        cin >> s;
        if (s == "push") {
            cin >> x;
            stk[++tt] = x;
        } else if (s == "pop") {
            tt--;
        } else if (s == "empty") {
            if (tt > 0) {
                cout << "NO" << endl;
            } else {
                cout << "YES" << endl;
            }
        } else if (s == "query") {
            cout << stk[tt] << endl;
        }
    }
    return 0;
}