10866번 - 덱

https://www.acmicpc.net/problem/10866

10866번: 덱

#include <iostream>
#include <string>
#include <deque>
using namespace std;
int main()
{
    int N, X;
    string str;
    deque<int> DQ;
    cin >> N;
    while(N--)
    {
        cin >> str;
        if(str == "push_front")
        {
            cin >> X;
            DQ.push_front(X);
        }
        else if(str == "push_back")
        {
            cin >> X;
            DQ.push_back(X);
        }
        else if(str == "pop_front")
        {
            if(DQ.empty())
                cout << -1 << '\n';
            else
            {
                cout << DQ.front() << '\n';
                DQ.pop_front();
            }
        }
        else if(str == "pop_back")
        {
            if(DQ.empty())
                cout << -1 << '\n';
            else
            {
                cout << DQ.back() << '\n';
                DQ.pop_back();
            }
        }
        else if(str == "size")
        {
            cout << DQ.size() << '\n';
        }
        else if(str == "empty")
        {
            if(!DQ.empty())
                cout << 0 << '\n';
            else
                cout << 1 << '\n';
        }
        else if(str == "front")
        {
            if(DQ.empty())
                cout << -1 << '\n';
            else
                cout << DQ.front() << '\n';
        }
        else if(str == "back")
        {
            if(DQ.empty())
                cout << -1 << '\n';
            else
                cout << DQ.back() << '\n';
        }
    }
    return 0;
}