Algorithm and program for Binary Search.

Binary search or half-interval search  algorithm compares the



 element to be search(i.e key)  with the middle element of the array. 



If the key is matched with the middle element ,it returns its 



position.and if not it divides the array into sub array according to 



the value of key. 



If the key value is greater than the value of middle element then 



the it will search the key from middle to right. 



If the key value is less than the value of middle element then the it 



will search the key from middle to left.



 It will repeat this action until no further division are possible or 



until the key matches with any of the element in array.


Binary search  Binary search 








/*....binary search program ......*/

#include <stdio.h>

   void main()


   {
   int arr[20];
   int i, low, mid, high, key, size;

   printf("Enter the size of an array\n");
   scanf("%d", &size);

   printf("Enter the  elements\n");
   for(i = 0; i < size; i++)
   {
    scanf("%d", &arr[i]);
   }

   printf("Enter the element to be search according to binary search\n");
   scanf("%d", &key);

   /*Binary search */

   low = 0;
   high = (size - 1);

   while(low <= high)
   {
    mid = (low + high)/2;
    if(key == arr[mid])
    {
     printf("element found at %d position \n",mid+1);
    return; 
    }
    if(key < table[mid])
     high = mid - 1;
    else
     low = mid + 1;
   }

   printf("element not found\n");


getch();
}       
Binary search  Binary search  Binary search  Binary search 

 Output

Enter the size of an array
5
Enter the array elements
12
36
45
78
99
Enter the key
45
element found at 3 position