78. Find Peak Element

A peak element is strictly greater than its neighbors. Given nums where nums[-1]=nums[n]=-∞, return any peak element index in O(log n) time.

Input: Integer array nums where no adjacent elements are equal.

Output: Index of any peak element.

Examples

Example 1

Input: [1,2,3,1]
Output: 2
Explanation: nums[2]=3>nums[1] and nums[3].

Example 2

Input: [1,2,1,3,5,6,4]
Output: 5
Explanation: nums[5]=6 is a peak.

Example 3

Input: [1]
Output: 0
Explanation: Single element is a peak.