binary search.java

// Java implementation of recursive
// Binary Search

class BinarySearch {

	// Function that returns index of
	// x if it is present in arr[l, r]
	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);
		}

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

	// Driver Code
	public static void main(String args[])
	{

		// Create object of this class
		BinarySearch ob = new BinarySearch();

		// Given array arr[]
		int arr[] = { 2, 3, 4, 10, 40 };
		int n = arr.length;
		int x = 10;

		// Function Call
		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);
	}
}