10845번 큐

#include <iostream>
#include <string>
#include <string.h>
#include <queue>

using namespace std;

void solve() {
	int inputNumber;
	int pushData;
	string command;
	queue<int> Queue;

	cin >> inputNumber;

	for (int i = 0; i < inputNumber; i++) {
		cin >> command;

		if (!command.compare("push")) {
			cin >> pushData;
			Queue.push(pushData);
		}
		else if (!command.compare("front")) {
			if (!Queue.size())
				cout << "-1" << endl;
			else
				cout << Queue.front() << endl;
		}
		else if (!command.compare("back")) {
			if (!Queue.size())
				cout << "-1" << endl;
			else
				cout << Queue.back() << endl;
		}
		else if (!command.compare("size")) {
			cout << Queue.size() << endl;
		}
		else if (!command.compare("empty")) {
			cout << Queue.empty() << endl;
		}
		else if (!command.compare("pop")) {
			if (!Queue.size())
				cout << "-1" << endl;
			else{
				cout << Queue.front() << endl;
				Queue.pop();
			}
		}
	}
}

int main() {
	solve();
	return 0;
}