C Example | Implement Binary Search (Recursive and Iterative)

This post will use two methods to implement binary search (Recursive and Iterative) using c language.

Recursive

#include <stdio.h>
int recursiveBinarySearch(int array[], int start_index, int end_index, int element){
   if (end_index >= start_index){
      int middle = start_index + (end_index - start_index )/2;
      if (array[middle] == element)
         return middle;
      if (array[middle] > element)
         return recursiveBinarySearch(array, start_index, middle-1, element);
      return recursiveBinarySearch(array, middle+1, end_index, element);
   }
   return -1;
}
int main(void){
   int array[] = {1, 4, 7, 9, 16, 56, 70};
   int n = 7;
   int element = 9;
   int found_index = recursiveBinarySearch(array, 0, n-1, element);
   if(found_index == -1 ) {
      printf("Element not found in the array ");
   }
   else {
      printf("Element found at index : %d",found_index);
   }
   return 0;
}

The output will be:

Element found at index : 3

Iterative

#include <stdio.h>
int iterativeBinarySearch(int array[], int start_index, int end_index, int element){
   while (start_index <= end_index){
      int middle = start_index + (end_index- start_index )/2;
      if (array[middle] == element)
         return middle;
      if (array[middle] < element)
         start_index = middle + 1;
      else
         end_index = middle - 1;
   }
   return -1;
}
int main(void){
   int array[] = {1, 4, 7, 9, 16, 56, 70};
   int n = 7;
   int element = 16;
   int found_index = iterativeBinarySearch(array, 0, n-1, element);
   if(found_index == -1 ) {
      printf("Element not found in the array ");
   }
   else {
      printf("Element found at index : %d",found_index);
   }
   return 0;
}

The output will be:

Element found at index : 4