[C++] 백준 10866번 덱

#include <iostream>
#include <deque>
#include <string>
using namespace std;
int main() {
	
	ios::sync_with_stdio(false);

	int testCase;
	cin >> testCase;

	deque<int> dq;

	for (int i = 0; i < testCase; i++) {
		string s;
		cin >> s;
		if (s == "push_front") {
			int num;
			cin >> num;
			dq.push_front(num);
		}
		else if (s == "push_back") {
			int num;
			cin >> num;
			dq.push_back(num);
		}
		else if (s == "pop_front") {
			if (dq.empty()) {
				cout << -1 << "\n";
			}
			else {
				cout << dq.front() << "\n";
				dq.pop_front();
			}
		}
		else if (s == "pop_back") {
			if (dq.empty()) {
				cout << -1 << "\n";
			}
			else {
				cout << dq.back() << "\n";
				dq.pop_back();
			}
		}
		else if (s == "size") {
			cout << dq.size() << "\n";
		}
		else if (s == "empty") {
			if (dq.empty()) {
				cout << 1 << "\n";
			}
			else {
				cout << 0 << "\n";
			}
		}
		else if (s == "front") {
			if (dq.empty()) {
				cout << -1 << "\n";
			}
			else {
				cout << dq.front() << "\n";
			}
		}
		else if (s == "back") {
			if (dq.empty()) {
				cout << -1 << "\n";
			}
			else {
				cout << dq.back() << "\n";
			}
		}
	}

	return 0;
}