Question

1. Write a binary search algorithm in C language by performing following steps:
2. Prompt the user to enter the number of array elements (say, N).  
3. Read the N different values (define these values to be of type integer).  
4. Read the element (integer value) which you want to search.
5. Invoke a function to display the values in the array. The function should take the array reference and number of elements as arguments and should have the return type as void. The function should loop through the array and print the array values one per line.
6. Invoke a function to search in the array using binary search (this function should take the array reference and number of elements as the arguments and the search element). The binary search function should have the return type as integer and it should return the array index when the search value is found, otherwise it should return -1.
7. The main program should print a message if the search value is found and the corresponding position in the array where it was found. If the search value was not found, then the main program should also print a message saying that the search value does not exist in the given array.

Answer 1

Binary search program:

//declare header file
#include <stdio.h>
//display_array function displays the array eleements
void display_array(int* a,int N){
int i=0;
printf("array eleements are:");
//traversing through array to print eleements
for(i=0;i<N;i++){
printf("%d\t",a[i]);
}
}
//binary_search function returns the search index in the array
int binary_search(int* a,int N,int k){
//declaration of variables
int first,last,middle;
  
first = 0;
last = N - 1;
middle = (first+last)/2;
//traversing through array
while (first <= last) {
//checking if the search element is less than mid value
if (a[middle] < k)
first = middle + 1;
//if the search element is found return the index of element
else if (a[middle] == k) {
return middle;
break;
}
else
last = middle - 1;

middle = (first + last)/2;
}
if (first > last)
return -1;
  
}
//start of main
int main()
{
//declaration of variables
int c,N,i,k;
//asking the user to enter array size
printf("Enter the number of elements");
scanf("%d",&N);
int a[N];
//asking the user to enter array elements
printf("enter array elements\n");
for(i=0;i<N;i++){
scanf("%d",&a[i]);
}
//prompting the user for search element
printf("\nEnter the element which you want to search:");
scanf("%d",&k);
//function calling
display_array(&a,N);
//storing the return value of binary_search function in c
c=binary_search(&a,N,k);
//printing the search element index
printf("\nkey element found at location:%d",c);
return 0;
}
OUTPUT:

NOTE:

1.There are warnings but the program will run successfully.