public class Solution
extends Object
852 - Peak Index in a Mountain Array\.
Easy
Let's call an array `arr` a **mountain** if the following properties hold:
* `arr.length >= 3`
* There exists some `i` with `0 < i < arr.length - 1` such that:
* `arr[0] < arr[1] < ... arr[i-1] < arr[i]`
* `arr[i] > arr[i+1] > ... > arr[arr.length - 1]`
Given an integer array `arr` that is **guaranteed** to be a mountain, return any `i` such that `arr[0] < arr[1] < ... arr[i - 1] < arr[i] > arr[i + 1] > ... > arr[arr.length - 1]`.
**Example 1:**
**Input:** arr = [0,1,0]
**Output:** 1
**Example 2:**
**Input:** arr = [0,2,1,0]
**Output:** 1
**Example 3:**
**Input:** arr = [0,10,5,2]
**Output:** 1
**Constraints:**
* 3 <= arr.length <= 104
* 0 <= arr[i] <= 106
* `arr` is **guaranteed** to be a mountain array.
**Follow up:** Finding the `O(n)` is straightforward, could you find an `O(log(n))` solution?