leetcode-162 Find Peak Element

[162] Find Peak Element

Key Concept: Binary Search on Unsorted Array - A peak exists if we always move toward the higher neighbor. Use binary search comparing mid with mid+1.

# Find a peak element in the array. Return any peak index.

class Solution:
    def findPeakElement(self, nums: List[int]) -> int:
        left, right = 0, len(nums) - 1

        while left < right:
            mid = (left + right) // 2

            if nums[mid] > nums[mid + 1]:
                # Peak is on the left (including mid)
                right = mid
            else:
                # Peak is on the right
                left = mid + 1

        return left

# Time: O(log n), Space: O(1)
# AirBnB: Tests binary search on non-sorted arrays