FindPeakElement.py

"""
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] = -∞. In other words, an element is always considered to be strictly greater than a neighbor that is outside the array.

You must write an algorithm that runs in O(log n) time.



Example 1:

Input: nums = [1,2,3,1]
Output: 2
Explanation: 3 is a peak element and your function should return the index number 2.
Example 2:

Input: nums = [1,2,1,3,5,6,4]
Output: 5
Explanation: Your function can return either index number 1 where the peak element is 2, or index number 5 where the peak element is 6.


Constraints:

1 <= nums.length <= 1000
-231 <= nums[i] <= 231 - 1
nums[i] != nums[i + 1] for all valid i.
"""


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

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

            if nums[mid] > nums[mid + 1]:
                # Move to the left side
                right = mid
            else:
                # Move to the right side
                left = mid + 1

        return left


# Example usage:
nums1 = [1, 2, 3, 1]
solution = Solution()
result1 = solution.findPeakElement(nums1)
print(result1)  # Output: 2

nums2 = [1, 2, 1, 3, 5, 6, 4]
result2 = solution.findPeakElement(nums2)
print(result2)  # Output: 5