백준 10845 큐,큐2 c++

[문제 링크]

https://www.acmicpc.net/problem/10845

10845번: 큐

https://www.acmicpc.net/problem/18258

18258번: 큐 2

 

[입출력 예]

입력	출력
15 push 1 push 2 front back empty pop pop pop size empty pop push 3 empty front	1 2 2 0 1 2 -1 0 1 -1 0 3

[소스코드]

#include <iostream>
#include <string>
#include <queue>
#define endl '\n'
using namespace std;

int main(void) {
  ios::sync_with_stdio(0);
  cin.tie(0);
  queue<int> Q;

  int n;
  cin>>n; // n 입력받음.

  string s;
  int x;
  while(n--){

    cin>>s;

    if (s=="push"){
       cin>>x;
      Q.push(x);
    }

    else if (s=="front"){
      if (Q.empty()) cout<<-1<<endl;
      else cout<<Q.front()<<endl;
    }
    else if (s=="size"){
      cout<<Q.size()<<endl;
    }
    else if (s=="back"){
      if (Q.empty()) cout<<-1<<endl;
      else cout<<Q.back()<<endl;
    }

    else if (s=="empty"){
      cout<<Q.empty()<<endl;
    }

    else if (s=="pop"){
      if (Q.empty()) cout<<-1<<endl;
      else {cout<<Q.front()<<endl;
      Q.pop();}
    }
  }

  return 0;
}