binarysearch.cpp

// C++ program to implement recursive Binary Search
 #include <bits/stdc++.h>
 using namespace std;

 // A recursive binary search function. It returns
 // location of x in given array arr[l..r] is present,
 // otherwise -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;
 }

 int main()
 {
 	int arr[] = { 2, 3, 4, 10, 40 };
 	int x = 10;
 	int n = sizeof(arr) / sizeof(arr[0]);
 	int result = binarySearch(arr, 0, n - 1, x);
 	if (result == -1)
 		cout << "Element is not present in array";
 	else
 		cout << "Element is present at index " << result;
 	return 0;
 }