162\. Find Peak Element

Medium

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

Given an 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] = -∞`.

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`
*   <code>-2<sup>31</sup> <= nums[i] <= 2<sup>31</sup> - 1</code>
*   `nums[i] != nums[i + 1]` for all valid `i`.