A program to implement the binary search algorithm.

#include <stdio.h>

void binary_search(const int *, const int, const int);

int main(void)
{
int arr[1000], i, v, cnt;

/* Store the values in the array */
for( i = 0; i < 1000; i++ )
arr[i] = 10 + i * 2;

printf( "\nEnter value to search : " );
scanf( "%d", &v );

binary_search(arr, v, 1000);

return 0;
}

void binary_search(const int *p, const int val, const int sz)
{
int fi, li, mi, n, found = 0;
/* Search the value in the array fi=first ,mi=milldle,li=last value */

n = 0;
fi = 0; /* Lowest subscript - will always be 0 */
li = sz - 1; /* Highest subscript - will be dimension - 1 */

if(val < p[fi] || val > p[li])
{
printf( "\n%d not found in the array", val);
printf( "\nNo of attempts = 1" );
}
else
{
printf( "\nAttempts\tFirst index\tLast index\tMiddle index\tarr[mi]" );
while(1)
{
n++;
/* Calculate middle index */
mi = (fi + li) / 2;

if( mi == fi || mi == li )
break; /* Processing complete */

printf( "\n\t%d\t%d\t\t%d\t\t%d\t\t%d", n, fi, li, mi, p[mi] );
if(val == p[mi] )
{
found = 1;
break;
}

if(val < p[mi])
{
li = mi;
continue;
}
if(val > p[mi])
{
fi = mi;
continue;
}
} /*End of while loop */
if(found)
{
printf( "\n%d found in the array", val);
printf( "\nNo of attempts = %d", n );
}
else
{
printf( "\n%d NOT found in the array", val);
printf( "\nNo of attempts = %d", n );
}
} /*End of else */
}