DSA/algorithms/CPlusPlus/Searching/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;
        //We use (l + (r - l)) rather than using (l + r) to avoid arithmetic overflow. 
        //Arithmetic overflow is the situation when the value of a variable increases
        //beyond the maximum value of the memory location, and wraps around.

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

        // If mid is greater than element, 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;
}