STL : 표준 템플릿 라이브러리
<queue> 사용
#include <iostream>
#include <vector>
#include<sstream>
#include <algorithm>
#include <string>
#include <utility>
#include <queue>
using namespace std;
int main() {
queue<int> s;
int N;
cin >> N;
for (int i = 0; i < N; i++) {
string command;
int num;
cin >> command;
if (command == "push") {
cin >> num;
s.push(num);
}
else if (command == "pop") {
if (s.empty()) {
cout << -1 << endl;
}
else {
cout << s.front() << endl;
s.pop();
}
}
else if (command == "size") {
cout << s.size() << endl;
}
else if (command == "empty") {
if (s.empty()) {
cout << 1 << endl;
}
else {
cout << 0 << endl;
}
}
else if (command == "front") {
if (s.empty()) {
cout << -1 << endl;
}
else {
cout << s.front() << endl;
}
}
else if (command == "back") {
if (s.empty()) {
cout << -1 << endl;
}
else {
cout << s.back() << endl;
}
}
}
}
