이진탐색

import java.util.Scanner; 
public class Main{ 
    public static int n,q; 
    public static int[] arr; 
    public static int[] qrr; 
    public static void main(String[] args){ 

      Scanner scan = new Scanner(System.in); 
      input(scan); 
       
      doSearch(); 
       
      scan.close(); 
    } 
     
     
    public static void doSearch() 
    { 
      for(int i=0;i<qrr.length;i++) 
      { 
        bSearch(qrr[i]); 
      } 
    } 
    public static void bSearch(int x) 
    { 
      int s = 0; 
      int e = arr.length-1; 
      if(x==arr[s] || x==arr[e]){System.out.println("YES");return;} 
      if(x<arr[s] || x>arr[e]){ System.out.println("NO");return;} 
       
      while(s+1<e) 
      { 
        int m = (s+e)/2; 
        if(arr[m]==x){System.out.println("YES");return;} 
        else if(arr[m]<x){s=m;} 
        else{e=m;} 
      } 
      System.out.println("NO"); 
    } 
     
     public static void bSearchRecursive(int s,int e,int x)
    {
  
        if(s>e){System.out.println("NO");return;}
      
        if(s==e)
        {
          if(arr[s]==x){System.out.println("YES");return;}
          else{System.out.println("NO");return;}
        }
        
        int m = (s+e)/2;
        if(arr[m]==x){System.out.println("YES");return;}
        else if(arr[m]<x)
        {bSearch(m+1,e,x);}
        else
        {bSearch(s,m-1,x);}
    }
     
     
    public static void input(Scanner scan) 
    { 
      n = scan.nextInt(); 
      q = scan.nextInt(); 
      arr = new int[n]; 
      qrr = new int[q]; 
      for(int i=0;i<n;i++)arr[i] = scan.nextInt(); 
      for(int i=0;i<q;i++)qrr[i] = scan.nextInt(); 
    } 
}

오랜만에 다시 풀었는데, 헤맸음.

경계로 범위를 좁혀가냐, 값으로 범위를 좁혀가냐 이거 잘 따져야 함.