Find Peak Element

medium

A peak element is an element that is strictly greater than its neighbors.

Given a 0-indexed integer array nums, find a peak element and return its index. If the array contains multiple peaks, return the index to any of the peaks.

You may imagine that nums[-1] = nums[n] = -∞. You must write an algorithm that runs in O(log n) time.

Test Cases

Copy an input into the main harness and Run to verify

Input

nums = [1,2,3,1]

Expected Output

2

Explanation: 3 is a peak element and your function should return index 2.

Input

nums = [1,2,1,3,5,6,4]

Expected Output

5

Explanation: Your function can return either index 1 or index 5.

Constraints

1 <= nums.length <= 1000
-2^31 <= nums[i] <= 2^31 - 1
nums[i] != nums[i + 1] for all valid i.

Hints

Hint 1 — click to reveal

O(log n) on unsorted data sounds impossible — but you only need *a* peak, not the largest.

Hint 2 — click to reveal

If the slope rises to the right, a peak must exist somewhere to the right.

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