w3resource

C Exercises: Find the pivot element of a sorted and rotated array using binary search

C Array: Exercise-37 with Solution

Write a program in C to find the pivot element of a sorted and rotated array using binary search.
Pivot element is the only element in input array which is smaller than it's previous element.
A pivot element divided a sorted rotated array into two monotonically increasing array.

Sample Solution:

C Code:

#include <stdio.h>
 
int findPivotElem(int *arr1, int left_elem, int right_elem)
{
   if (right_elem < left_elem)   
       return -1;
   if (right_elem == left_elem) 
       return left_elem;
   int mid_elem = (left_elem + right_elem)/2;
   if (mid_elem < right_elem && arr1[mid_elem] > arr1[mid_elem + 1])
       return mid_elem;
   if (mid_elem > left_elem && arr1[mid_elem] < arr1[mid_elem - 1])
       return mid_elem-1;
   if (arr1[left_elem] >= arr1[mid_elem])
   {
       return findPivotElem(arr1, left_elem, mid_elem-1);
   } else 
   {
       return findPivotElem(arr1, mid_elem + 1, right_elem);
   }
}
int main()
{
    int i;
    int arr1[] = {14, 23, 7, 9, 3, 6, 18, 22, 16, 36};
    int ctr = sizeof(arr1)/sizeof(arr1[0]);
    printf("The given array is :  ");
	for(i = 0; i < ctr; i++)
	{
	printf("%d  ", arr1[i]);
    } 
    printf("\n");
    printf("The Pivot Element in the array is : %d \n", arr1[findPivotElem(arr1, 0, ctr-1) + 1]);
    return 0;
}

Sample Output:

The given array is :  14  23  7  9  3  6  18  22  16  36  
The Pivot Element in the array is : 3 

Flowchart :

Flowchart: Find the pivot element of a sorted and rotated array using binary search.

C Programming Code Editor:

Improve this sample solution and post your code through Disqus.

Previous: Write a program in C to find the missing number from a given array. There are no duplicates in list.
Next: Write a program in C to merge one sorted array into another sorted array.

What is the difficulty level of this exercise?



Inviting useful, relevant, well-written and unique guest posts