Ps_algorithm/10845bj.cpp at main · chanik-s/Ps_algorithm · GitHub

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

int main() {
	ios::sync_with_stdio(0);
	cin.tie(0);
	int n;
	cin >> n;
	queue <int> q;
	while (n--) {

		string op;
		cin >> op;


		if (op == "push") {
			int x;
			cin >> x;

			q.push(x);
		}
		else if (op == "pop") {
			if (!q.empty()) {
				cout << q.front() << '\n';
				q.pop();
			}
			else cout << -1 << '\n';
		}
		else if (op == "size") {
			cout << q.size() << '\n';
		}
		else if (op == "empty") {
			if (q.empty()) cout << 1 << '\n';
			else cout << 0 << '\n';
		}
		else if (op == "front") {
			if (!q.empty()) {
				cout << q.front() << '\n';
			}
			else {
				cout << -1 << '\n';
			}
		}
		else { //back
			if (!q.empty()) {
				cout << q.back() << '\n';
			}
			else {
				cout << -1 << '\n';
			}
		}

	}

	return 0;
}