426. Find Smallest Element Index

Given a sorted array of integers nums which is rotated at some unknown pivot point (e.g., [0,1,2,4,5,6,7] might become [4,5,6,7,0,1,2]). Your task is to find the index of the smallest element in this array. You must write an algorithm with $O(\log n)$ runtime complexity, utilizing binary search.

Example:
Input: nums = [4,5,6,7,0,1,2]
Output: 4 (The smallest element 0 is at index 4)

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