#include <stdio.h>
 
int RecBinarySearch(int arr[], int len, int target) {
	if(len <= 0) return -1;
	int mid = len / 2;
	if(arr[mid] == target) return mid;
	if(arr[mid] < target) {
		int rightIndex = RecBinarySearch(arr+mid+1, len-mid-1, target);
		return rightIndex == -1 ? -1 : mid+rightIndex+1;
	} else {
		int leftIndex = RecBinarySearch(arr, mid, target);
		return leftIndex == -1 ? -1 : leftIndex;
	}
}
 
int main(void){
    int arr[6]={1,2,3,4,5,6};
    int len=sizeof(arr)/sizeof(arr[0]);
    int target = 5;
    printf("%d", RecBinarySearch(arr,len,target));
}

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