にぶんほうアルゴリズム

public class TestBinarySearch {
	public static void main(String[] args) {
        int [] array = {1,7,9,25,64,98};
        int index1 = binarySearch(9,array,0,array.length);
        System.out.println("Index : "+index1);
        int index2 = binarySearch2(array,9,0,array.length);
        System.out.println("Index : "+index2);
    }	
    
    public static int binarySearch(int elem,int array [],int low,int high){
        if(low>high)return -1;
        int mid = (low+high)/2;
        if(array[mid] == elem)return mid;
        if(array[mid] < elem) return binarySearch(elem,array,mid+1,high);
        if(array[mid] > elem) return binarySearch(elem, array, low, mid-1);
        return -1;
    }
    
    public static int binarySearch2(int[] data,int goal,int left,int right){
        int mid = (left+right)/2 ;   
        if(left>right){    
            return -1 ;     
        }        
        if(goal==data[mid]){   
            return mid ;
        }  
        else if(goal<data[mid]){ 
            //  right = mid -1 ; 
            return binarySearch2(data,goal,left,mid-1);
        } 
        else if(goal>data[mid]){        
            return binarySearch2(data,goal,mid+1,right);
        }  
        return -1 ;         
    }       
}