[백준]10845-큐(설명X)

#include <iostream>
#include <queue>
using namespace std;
 
int main() {
    int command;
    cin >> command;
    queue<int> que;
    for (size_t i = 0; i < command; i++) {
        string str;
        cin >> str;
        if (!str.compare("pop")) {
            int size = que.size();
            if (size > 0) {
                cout << que.front() << endl;
                que.pop();
            }
            else
                cout << -1 << endl;
        }
        else if (!str.compare("size")) {
            cout << que.size() << endl;
        }
        else if (!str.compare("empty")) {
            if (que.empty())
                cout << 1 << endl;
            else
                cout << 0 << endl;
        }
        else if (!str.compare("front")) {
            int size = que.size();
            if (size > 0)
                cout << que.front() << endl;
            else
                cout << -1 << endl;
        }
        else if (!str.compare("back")) {
            int size = que.size();
            if (size > 0)
                cout << que.back() << endl;
            else
                cout << -1 << endl;
        }
        else {
            int num;
            cin >> num;
            que.push(num);
        }
    }
    return 0;
}