[백준] 10828번 스택 C++ 풀이법

https://www.acmicpc.net/problem/10828

#include<iostream>
#include<stack>
#include<string>
 
using namespace std;
 
int main()
{
    stack <int> st;
    int N;
    string order;
 
    cin >> N;
    for (int i = 0; i < N; i++)
    {
        cin >> order;
        if (order == "push")
        {
            int X;
            cin >> X;
            st.push(X);
        }
        else if (order == "pop")
        {
            if (st.empty() == true)
            {
                cout << -1 << "\n";
            }
            else 
            {
                cout << st.top() << "\n";
                st.pop();
            }
        }
        else if (order == "size")
        {
            cout << st.size() << "\n";
        }
        else if (order == "empty")
        {
            cout << st.empty() << "\n";
        }
        else if (order == "top")
        {
            if (st.empty() == true) cout << -1 << "\n";
            else cout << st.top() << "\n";
        }
    }
}