TheAlgorithms-C/searching/binary_search.c

#include <stdio.h>

// Recursive Function- It returns location of x assumiung 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 element is present at middle
        if (arr[mid] == x)
            return mid;

        // If element is smaller than middle
        if (arr[mid] > x)
            return binarysearch(arr, l, mid - 1, x);

        // Else element is in right subarray
        return binarysearch(arr, mid + 1, r, x);
    }

    // When element is not present in array
    return -1;
}

int main(void)
{
    // give function an array to work with
    int arr[] = {2, 3, 4, 10, 40};
    // get size of array
    int n = sizeof(arr) / sizeof(arr[0]);
    // set value to look for
    int x = 10;
    // set result to what is returned from binarysearch
    int result = binarysearch(arr, 0, n - 1, x);
    // print out result
    (result == -1) ? printf("Element is not in the array\n")
                   : printf("Element is present at index %d\n", result);
    return 0;
}