## Description

https://leetcode.com/problems/find-peak-element/

A peak element is an element that is greater than its neighbors.

Given an input array `nums`

, where `nums[i] ≠ nums[i+1]`

, find a peak element and return its index.

The array may contain multiple peaks, in that case return the index to any one of the peaks is fine.

You may imagine that `nums[-1] = nums[n] = -∞`

.

**Example 1:**

Input:nums=`[1,2,3,1]`

Output:2Explanation: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:1 or 5Explanation:Your function can return either index number 1 where the peak element is 2, or index number 5 where the peak element is 6.

**Note:**

Your solution should be in logarithmic complexity.

## Explanation

Use binary search to find

## Python Solution

```
class Solution:
def findPeakElement(self, nums: List[int]) -> int:
start = 0
end = len(nums) - 1
while start + 1 < end:
mid = start + (end - start) // 2
if nums[mid - 1] < nums[mid] and nums[mid] > nums[mid + 1]:
return mid
elif nums[mid - 1] > nums[mid]:
end = mid
elif nums[mid] < nums[mid + 1]:
start = mid
if nums[end] > nums[start]:
return end
return start
```

- Time complexity: O(log(N)).
- Space complexity: O(1).

## One Thought to “LeetCode 162. Find Peak Element”