02_binary_search.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(void) 
{ 
	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); 
	(result == -1) ? cout << "Element is not present in array"
				: cout << "Element is present at index " << result; 
	return 0; 
}