[백준] 10845번 : 큐

10845번: 큐

 

#include <iostream>
#include<vector>
#include<algorithm>
#include<queue>
#include<string>
using namespace std;

int main() {

	ios_base::sync_with_stdio(false);
	cin.tie(NULL);

	int n, k;
	string s;
	queue<int>q;

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

		cin >> s;

		if (s == "push") {
			cin >> k;
			q.push(k);
		}

		else if (s == "front") {
			if (q.size() != 0)
				cout << q.front() << '\n';
			else cout << -1 << '\n';
		}

		else if (s == "size") {
			cout << q.size() << '\n';
		}

		else if (s == "pop") {
			if (q.size() != 0) {
				cout << q.front() << '\n';
				q.pop();
			}
			else cout << -1 << '\n';
		}

		else if (s == "empty") {
			if (q.empty())
				cout << 1 << '\n';
			else cout << 0 << '\n';
		}

		else if (s == "back") {
			if (q.empty())
				cout << -1 << '\n';
			else cout << q.back() << '\n';
		}
	}
}