Grokking the Coding Interview: Patterns for Coding Questions
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Problem Challenge 3: Rotation Count (medium)
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Problem Statement

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Problem Statement

Given an array of numbers which is sorted in ascending order and is rotated ‘k’ times around a pivot, find ‘k’.

You can assume that the array does not have any duplicates.

Note: You need to solve the problem in O(logn) time complexity.

Example 1:

Input: [10, 15, 1, 3, 8]
Output: 2
Explanation: The array has been rotated 2 times.
Image

Example 2:

Input: [4, 5, 7, 9, 10, -1, 2]
Output: 5
Explanation: The array has been rotated 5 times.
Image

Example 3:

Input: [1, 3, 8, 10]
Output: 0
Explanation: The array has not been rotated.

Constraints:

  • 1 <= arr.length <= 5000
  • -10<sup>4</sup> <= arr[i] <= 10<sup>4</sup>
  • All values of nums are unique.
  • arr is an ascending array that is possibly rotated.

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Try solving this question here:

Python3
Python3
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Problem Statement

Try it yourself