백준 10845번: 큐

https://www.acmicpc.net/problem/10845

📌문제 접근

1. queue STL사용
2. push X의 경우 버퍼를 이용하여 처리

#include <iostream>
#include <queue>
#include <string>
#include <cstring>
using namespace std;

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    queue<int> q;
    int num;
    cin >> num;
    while(num--)
    {
        string str;
        cin >> str;

        if(str == "push"){
           int n;
           cin >> n;
           q.push(n);
        }
        else if(str == "pop")
        {
            if(q.empty())
                cout << -1 << endl;
            else
            {
                cout << q.front() << endl;
                q.pop();
            }
        }
        else if(str == "front")
        {
            if(q.empty())
                cout << -1 << endl;
            else
                cout << q.front() << endl;
        }
        else if(str == "back")
        {
            if(q.empty())
                cout << -1 << endl;
            else
                cout << q.back() << endl;
        }
        else if(str == "size")
        {
            cout << q.size() << endl;
        }
        else if(str == "empty")
        {
            if(q.empty())
                cout << 1 << endl;
            else
                cout << 0 << endl;
        }
    }
}