C program to binary search using recursion

C program to binary search using recursion


Input:
5
1 2 3 4 5
3

Output:
3 is found

Implementation:

/* 
 Source: http://www.coderegister.co.in/2015/07/binary-search-to-search-element-in-array.html
*/
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>

/* Binary search to search an element in the array */
int binarysearch(int *a,int l,int r,int e)
{
 int mid;
 if(l<r)
 {
  
  /* Calculate the middle index of the array */
  mid=(l+r)/2;
  
  /* If the middle element is the element we are searching, return the middle index */
  if(*(a+mid)==e)
   return 1;
  
  /* Else recur for starting index to mid-1 */
  else if(e<*(a+mid))
   return binarysearch(a,l,mid-1,e);
  
  /* Else recur for mid+1 index to end */
  else
   return binarysearch(a,mid+1,r,e);
 }
 return 0;
}

int main(void) {
 int *a,n,i,element;
 
 /* allocate the memory */
 a=(int*)malloc(sizeof(int)*100);
 
 /* get the number of elements of the array */
 scanf("%d",&n);
 
 /* get the elements of the array */
 for(i=0;i<n;i++)
  scanf("%d",(a+i));
 
 /* Get the element to search in the array */
 scanf("%d",&element);
 
 /* If the function return value is true, then the element is in the array */
 if(binarysearch(a,0,n,element))
  printf("%d is found",element);
 
 /* else the element is not found in the array */
 else
  printf("%d is not found",element);
  
 return 0;
}