This C program, using recursion, performs binary search. In this program an array of random number is generated. The user is asked to enter a key. The array of random numbers are sorted and then the binary search operation is performed based on the key.

Here is the source code of the C program to display a linked list in reverse. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

/*
* C Program to Perform Binary Search using Recursion
*/
#include <stdio.h>

void binary_search(int [], int, int, int);
void bubble_sort(int [], int);

int main()
{
int key, size, i;
int list[25];

printf("Enter size of a list: ");
scanf("%d", &size);
printf("Generating random numbers\n");
for(i = 0; i < size; i++)
{
list[i] = rand() % 100;
printf("%d ", list[i]);
}
bubble_sort(list, size);
printf("\n\n");
printf("Enter key to search\n");
scanf("%d", &key);
binary_search(list, 0, size, key);

}

void bubble_sort(int list[], int size)
{
int temp, i, j;
for (i = 0; i < size; i++)
{
for (j = i; j < size; j++)
{
if (list[i] > list[j])
{
temp = list[i];
list[i] = list[j];
list[j] = temp;
}
}
}
}

void binary_search(int list[], int lo, int hi, int key)
{
int mid;

if (lo > hi)
{
printf("Key not found\n");
return;
}
mid = (lo + hi) / 2;
if (list[mid] == key)
{
printf("Key found\n");
}
else if (list[mid] > key)
{
binary_search(list, lo, mid - 1, key);
}
else if (list[mid] < key)
{
binary_search(list, mid + 1, hi, key);
}
}}

$ gcc binary_search.c -o binary_search
$ a.out
Enter size of a list: 10
Generating random numbers
83 86 77 15 93 35 86 92 49 21

Enter key to search
21
Key found