binarySearch.cpp

#include <bits/stdc++.h>
using namespace std;

// A iterative binary search function. It returns
// location of x in given array arr[l..r] if present,
// otherwise -1
int binarySearch(int arr[], int l, int r, int x)
{
	while (l <= r) {
		int m = l + (r - l) / 2;

		// Check if x is present at mid
		if (arr[m] == x)
			return m;

		// If x greater, ignore left half
		else if (arr[m] < x) //in case of else if, if the upper condition is true, this one will not run
			l = m + 1;

		// If x is smaller, ignore right half
		else
			r = m - 1;
	}

	// if we reach here, then element was
	// not present
	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);
	if(result == -1)
		 cout << "Element is not present in array";
	else
                 cout << "Element is present at index " << result;
	return 0;
}