Question

(Recursive Binary Search) Write a recursive method recursiveBinarySearch to perform a binary search of an array. The method should receive the search key, starting index and ending index as arguments. If the search key is found, return its index in the array. If the search key is not found, return –1. (NOTE: Complete the recursiveBinarySearch method in the BinaryArray class). java

Answer 1

public class Main
{
static int recursiveBinarySearch(int arr[], int l, int r, int x)
{
       //inputs
       //arr:array
       //x:search key
       //l:starting index
       //r:ending index
if (r >= l)
       {
int mid = l + (r - l) / 2; //finding mid value
  
if (arr[mid] == x) //matching with x
return mid; //if matches then returning index
  
if (arr[mid] > x) //if less than current mid value
return recursiveBinarySearch(arr, l, mid - 1, x);//then selecting left subarray
  
return recursiveBinarySearch(arr, mid + 1, r, x); //selecting right subarray
}

return -1;
}
  
   public static void main(String[] args) {
   //testing above function
   int arr[] = { 1,2,2, 3, 4, 10, 40 };
int n = arr.length;
int x = 10;
int result = recursiveBinarySearch(arr, 0, n - 1, x);
       if (result == -1)
System.out.println("Element not present");
else
System.out.println("Element found at index " + result);
   }
}

output:

Element found at index 5