code3_binary_search_recursive.java

// Java implementation of recursive Binary Search
class BinarySearch
{
	// Returns index of x if it is present in arr[l..r], else
	// return -1
	int binarySearch(int arr[], int l, int r, int x)
	{
		if (r>=l)
		{
			int mid = l + (r - l)/2;

			// If the element is present at the middle itself
			if (arr[mid] == x)
			return mid;

			// If element is smaller than mid, then it can only
			// be present in left subarray
			if (arr[mid] > x)
			return binarySearch(arr, l, mid-1, x);

			// Else the element can only be present in right
			// subarray
			return binarySearch(arr, mid+1, r, x);
		}

		// We reach here when element is not present in array
		return -1;
	}

	// Driver method to test above
	public static void main(String args[])
	{
		BinarySearch ob = new BinarySearch();
		int arr[] = {2,3,4,10,40};
		int n = arr.length;
		int x = 10;
		int result = ob.binarySearch(arr,0,n-1,x);
		if (result == -1)
			System.out.println("Element not present");
		else
			System.out.println("Element found at index "+result);
	}
}