C++(씨쁠쁠)(cplusplus)-백준(baekjoon)(BaekJoon)코딩 10866번:덱 답

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