<algorithm> 1. Queue

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

import java.util.LinkedList;

import java.util.Queue;

import java.util.Scanner;

public class Main {

br />

@SuppressWarnings("resource")

public static void main(String[] args) {

// TODO Auto-generated method stub

Queue<Integer> qu=new LinkedList<Integer>();

Scanner sc=new Scanner(System.in);

Scanner sc2=new Scanner(System.in);

int k=Integer.parseInt(sc.next());

int back=-1;

for(int i=0;i<k;i++){

String k1=sc2.nextLine();

if(k1.substring(0, 3).equals("pus")){

String[] k2=k1.split(" ");

qu.offer(Integer.parseInt(k2[1]));

back=Integer.parseInt(k2[1]);

}

if(k1.equals("front")){

 

System.out.println(qu.peek());

 

}if(k1.equals("back")){

System.out.println(back);

}

if(k1.equals("size")){

System.out.println(qu.size());

}

if(k1.equals("empty")){

System.out.println(qu.isEmpty()?1:0);

}

if(k1.equals("pop")){

if(qu.size()==0){

back=-1;

System.out.println(back);

}

else

System.out.println(qu.poll());

}

}

}

}

예제는 맞는데 왜 런타임 오류가 뜨는지 모르겠다..