# Leetcode 852 - Peak Index in a Mountain Array

`Note:`

- Because arr is guaranteed to be a mountain array, we only need to find the first element that is bigger than both of its neighbor.

`Question:`

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] |

`Code:`

1 | /** |