Find Peak Element

Locate any index where the element is strictly greater than its neighbors.

arrays search binary-search

A peak element is an element that is strictly greater than its neighbors. Given an integer array `nums`, implement the function `find_peak_element(nums: list[int]) -> int` that returns the index of any peak element. You may imagine that `nums[-1] = nums[n] = -infinity` (i.e., the element at index 0 is a peak if it is greater than `nums[1]`, and the element at the last index is a peak if it is greater than `nums[n-2]`). The array may contain multiple peaks; your function can return the index of any of them.

Constraints

1 <= len(nums) <= 10^5
-10^9 <= nums[i] <= 10^9
There is guaranteed to be at least one peak element.
Your solution should run in O(log n) time.

Example

find_peak_element([1,2,3,1]) -> 2
find_peak_element([1,2,1,3,5,6,4]) -> 5  # 1 is also acceptable

20 points ~25 min

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Hints

Think about the slope between adjacent elements: if nums[mid] < nums[mid+1], the peak is to the right; else the peak is to the left (including mid).

Use binary search to reduce the search range in half each step.

The boundary conditions are handled by assuming -infinity outside the array.

Test Results

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