> ## Documentation Index
> Fetch the complete documentation index at: https://leetcode-py.wisl.dev/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> leetcode-py is a Python LeetCode practice environment generator with one CLI: lcpy. It is not a service or platform.
> Each problem is a directory under leetcode/ with README.md, solution.py, test_solution.py, helpers.py, and playground.ipynb. lcpy gen creates them from JSON templates bundled with the package.
> Examples are backed by tests; copy them verbatim.

# Find Peak Element Python Solution with Tests

> Tested Python solution for LeetCode 162 with 16 pytest cases. Generate a practice environment with lcpy.

LeetCode 162, [Medium](/catalog/medium). Topics: [Array](/catalog/topics/array), [Binary Search](/catalog/topics/binary-search). [View on LeetCode](https://leetcode.com/problems/find-peak-element/description/).

Generate this problem as a practice environment: tested reference solution, 16 [parametrized pytest cases](/practice/testing), and a playground notebook:

```bash theme={"theme":{"light":"github-light","dark":"github-dark"}}
lcpy gen -n 162   # by problem number
lcpy gen -s find_peak_element   # by problem name
```

## 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. 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.

### Examples

```
Input: nums = [1,2,3,1]
Output: 2
Explanation: 3 is a peak element and your function should return the index number 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
* -2\<sup>31\</sup> \<= nums\[i] \<= 2\<sup>31\</sup> - 1
* `nums[i] != nums[i + 1]` for all valid `i`.

## Solution

Reference implementation from [solution.py on GitHub](https://github.com/wislertt/leetcode-py/blob/main/leetcode/find_peak_element/solution.py), full suite in [test\_solution.py](https://github.com/wislertt/leetcode-py/blob/main/leetcode/find_peak_element/test_solution.py):

```python theme={"theme":{"light":"github-light","dark":"github-dark"}}
class Solution:
    # Time: O(log n)
    # Space: O(1)
    def find_peak_element(self, nums: list[int]) -> int:
        left, right = 0, len(nums) - 1
        while left < right:
            mid = (left + right) // 2
            if nums[mid] > nums[mid + 1]:
                right = mid
            else:
                left = mid + 1
        return left
```

## Complexity

| Time | Space |
| - | - |
| O(log n) | O(1) |

## Tags

[NeetCode All](/catalog/neetcode).


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