How to find the smallest element in an array using binary search algorithm in C language?

The C programming language provides two search techniques. They are as follows:

• Linear search
• Binary search

Binary search

• This method only works for Ordered list.
• The given list is divided into two equal parts.
• The given keyword is compared to the middle element of the list.

Here, three things can happen, as follows:

• If the middle element matches the keyword, the search will end successfully here

• If the middle element is larger than the keyword, the search will be performed on the left partition.

• If the middle element is smaller than the keyword, the search will be performed on the right partition.

Input (i/p) - Unsorted list of elements, keyword.

Output (o/p) -

• Success - If keyword found
• Failure - Otherwise

key = 20
mid = (low +high) /2

Program 1

The following is a C program to find the smallest element in an array using binary search:

#include<stdio.h>
int main(){
   int a[50], n, i, key, flag = 0, low, mid, high;
   printf("enter the no: of elements:");
   scanf ("%d",&n);
   printf("enter the elements:");
   for(i=0; i<n; i++)
      scanf( "%d", &a[i]);
   printf("enter a key element:");
   scanf ("%d", &key);
   low = 0;
   high = n-1;
   while (low<= high ){
      mid = (low + high) /2;
      if (a[mid] == key){
         flag = 1;
         break;
      }
      else{
         if (a[mid] > key)
            high = mid-1;
         else
            low = mid+1;
      }
   }
   if (flag == 1)
      printf ("search is successful");
   else
      printf("search is unsuccessful");
   return 0;
}

Output

When the above program is executed, it produces the following result −

Run 1:
enter the no: of elements:5
enter the elements:
12
34
11
56
67
enter a key element:45
search is unsuccessful
Run 2:
enter the no: of elements:3
enter the elements:
12
34
56
enter a key element:34
search is successful

Program2

Given the following C program, it is found by using binary search Minimum element in the array −

#include<stdio.h>
void Bmin(int *a, int i, int n){
   int j, temp;
   temp = a[i];
   j = 2 * i;
   while (j <= n){
      if (j < n && a[j+1] > a[j])
         j = j + 1;
      if (temp < a[j])
         break;
      else if (temp >= a[j]){
         a[j / 2] = a[j];
         j = 2 * j;
      }
   }
   a[j/2] = temp;
   return;
}
int binarysearchmin(int *a,int n){
   int i;
   for(i = n/2; i >= 1; i--){
      Bmin(a,i,n);
   }
   return a[1];
}
int main(){
   int n, i, x, min;
   int a[20];
   printf("Enter no of elements in an array</p><p>");
   scanf("%d", &n);
   printf("</p><p>Enter %d elements: ", n);
   for (i = 1; i <= n; i++){
      scanf("%d", &a[i]);
   }
   min = binarysearchmin(a, n);
   printf("\minimum element in an array is : %d", min);
   return 0;
}

Output

When the above program is executed, it produces the following result−

Enter no of elements in an array
5
Enter 5 elements:
12
23
34
45
56
minimum element in an array is: 12

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