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`