Find Peak Element — LeetCode 162 Python Solution

The problem

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.

Example

Input

nums = [1,2,3,1]

Output

2

Explanation

3 is a peak element and your function should return the index number 2.

Python solution

class Solution:
    def findPeakElement(self, nums: List[int]) -> int:
        left, right = 0, len(nums) - 1
        while left < right:
            mid = (left + right) >> 1
            if nums[mid] > nums[mid + 1]:
                right = mid
            else:
                left = mid + 1
        return left

Complexity

Pattern: Monotonic Stack

Answer "what is the next greater element" for every position in one pass. LeetCode 162. Find Peak Element is filed here because the reference solution below belongs to the algorithm family this hub collects, even though its LeetCode tags point elsewhere.

The monotonic stack guide has the Python template for the pattern and the 225 LeetCode problems that use it.

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