/* Author:Yana

Module: binsearch.c

What:

-----

Searching a number in SORTED array

and returning its location if found.

Input: N integers separated by a space from

each other, followed by the number

to search.

Output: The location of the number, if found

or an appropriate message otherwise.

Assumption on input: valid.

How

-----

Algorithm: binary search

*/

#include < stdio.h >

#defne SIZE 10 /* size of input */

/* function prototypes */

int BinarySearch (int A[], int low, int high, int val) ;

int main (){

int array[SIZE]; /* array for input */
int i; /* index in the array */
int number; /* A number to search */
int location; /* Location of number in list, if exists, -1 if doesn't exist */

/* read input */
printf("Please enter %d integers \n" , SIZE);
for (i = 0; i < SIZE; i++){
scanf("%d", &array[i] );
}

printf("\nPlease enter a number to locate: ");
scanf("%d", &number);

/* locate number */
location = BinarySearch(array, 0, SIZE - 1, number);
if (location != -1 )
printf("The value %d appears in place %d \n", number, location );
else

printf("The value %d is not in the given array\n ", number);

return 0;

}

/* BinarySearch: Search a given number in an array of numbers.

Parameters: A - array to search

low - low limit

high - high limit

val - value to search

Returns: the index of the searched element in the array or -1 if the element is not in the array

Algorithm: BinarySearch */

int BinarySearch (int A[], int low, int high, int val){

int middle;

while (low <= high ) {
middle = (low + high) /2;
if (val == A [ middle ] ){
return middle;
}
else if ( val < A [ middle ] )
high = middle - 1;
else
low = middle + 1;
}
return -1;

}