find_peak_element.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.

class Solution:
    def findPeakElement(self, nums: List[int]) -> int:
        if len(nums) == 1:
            return 0
        first_el = nums[0]
        for i in range(len(nums)):
            if i == 0:
                first_el = nums[i]
                continue
            elif i == len(nums)-1:
                if nums[i] > nums[i-1]:
                    if first_el > nums[i] and first_el > nums[1]:
                        return 0
                    return i
                elif nums[i-1] > nums[i]:
                    if first_el > nums[i-1] and first_el > nums[1]:
                        return 0
                    return i-1
            if nums[i] > nums[i-1] and nums[i] > nums[i+1]:
                return i
        
        return -7777