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.