Binary Search Program using C Programming Language

 #include   <stdio.h>

#include   <stdlib.h>

int  binarySearch( int  *A,  int  n,  int  key);

int  main() {

printf( "Binary Search \n" );

printf( "\n" );

int  i, n, key, index;

printf( "Total Elements : " );

scanf( "%d" , &n);

printf( "\n" );

if  (n < 1) {

printf( "Invalid Input \n" );

printf( "\n" );

return  1;

}

int  *A = ( int  *)calloc(n,  sizeof ( int ));

printf( "Number Input (Sorted Order)\n" );

for  (i = 0; i < n; i++) {

scanf( "%d" , (A + i));

if  (i > 0 && *(A + (i - 1)) > *(A + i)) {

printf( "Input Not Sorted \n" );

printf( "\n" );

return  1;

}

}

printf( "\n" );

printf( "Number to be Searched : " );

scanf( "%d" , &key);

printf( "\n" );

index = binarySearch(A, n, key);

if  (index == -1) {

printf( "Number (%d) not found \n" , key);

}

else  {

printf( "Number (%d) found at Index : %d \n" , key, index);

}

printf( "\n" );

return  0;

}

int  binarySearch( int  * A ,  int   n ,  int   key ) {

int  p = 0, q, r = ( n -1);

while  (p < r) {

q = (p + r) / 2;

if  ( key  == *( A  + q)) {

return  q;

}

else   if  ( key  > *( A  + q)) {

p = q + 1;

}

else  {

r = q - 1;

}

}

return  -1;

}