Recursive Binary Search Array out of Index

Question

public static void main(String[] args) {
    int [] arr = {11,14,18,22,36,89,125};
    System.out.println(recursive_binary_search(arr,0,arr.length,989));

}


public static int recursive_binary_search(int[] A,int p,int r,int x) {

    if( p > r) {

        return -1;
    }else {
        int q=(p+r)/2;
        if(A[q]==x) {

            return q;
        }else if(A[q]>x) {

            return recursive_binary_search(A,p,q-1,x);
        }else {
            return recursive_binary_search(A,q+1,r,x);

        }


    }


}

Hey, thank you for reading. I am having some problem with this recursive binary search method. When I try to search something that is not in the array, java give me "Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 7".

I thought it should return -1 because of the p>r condition. I tried to change the condition to p>=r but then it would return -1 for things that are actually present in array. What am I doing wrong? Thank you so much

Answer 1

搜索应从0到arr.length-1 ，

System.out.println(recursive_binary_search(arr,0,arr.length-1,989));