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

Given an input array wherenum[i] ≠ num[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 thatnum[-1] = num[n] = -∞.

For example, in array[1, 2, 3, 1], 3 is a peak element and your function should return the index number 2.

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Credits:
Special thanks to@tsfor adding this problem and creating all test cases.

tag: binary search

class Solution {
    public int findPeakElement(int[] nums) {
        int left = 0, right = nums.length - 1;

        while (left + 1 < right){
            int mid = left + (right - left) / 2;

            if (nums[mid] < nums[mid + 1]){
                left = mid;
            }
            else if (nums[mid] < nums[mid - 1]){
                right = mid;
            }
            else if (nums[mid] > nums[mid - 1] && nums[mid] > nums[mid + 1]){
                return mid;
            }


        }

        if (nums[left] > nums[right]){
            return left;
        }
        else{
            return right;
        }
    }
}