C language binary search

binary search is also known as Binary retrieval; Split half search method; Binary search.

It is to search in sorted data.

#include <stdio.h>
  
// Find the position of x in the array arr[l..r]
// If not found, return -1
int binarySearch(int arr[], int l, int r, int x)
{
    if (r >= l) {
        int mid = l + (r - l) / 2;
  
        // in the middle exactly  
        if (arr[mid] == x)
            return mid;
  
        // If the value is less than the middle value, then continue searching in the left half part
        if (arr[mid] > x)
            return binarySearch(arr, l, mid - 1, x);
  
        // If the value is greater than the middle value, continue searching in the right half part
        return binarySearch(arr, mid + 1, r, x);
    }
  
    // not found
    return -1;
}
  
int main(void)
{
    int arr[] = { 2, 3, 4, 10, 40 };
    int n = sizeof(arr) / sizeof(arr[0]);
    int x = 10;
    int result = binarySearch(arr, 0, n - 1, x);
    (result == -1)
        ? printf("not found")
        : printf("find x at ： %d", result);
    return 0;
}