# Find Peak Element

Given an integer array `A`

, a peak element with index `p`

is defined as `A[p] > A[p - 1] && A[p] > A[p + 1]`

. Find a peak element in this array and return its index. The array may contains multiple peeks; return any of them.

Note, the array has the following properties:

- The numbers in adjacent positions are different.
- A[0] < A[1] && A[A.length - 2] > A[A.length - 1].

Example

Given `[1, 2, 1, 3, 4, 5, 7, 6]`

Return index `1`

(which is number 2) or `6`

(which is number 7)

The following solution has O(n) time-complexity.