Valid Mountain Array

Given an array of integers arr, return true if and only if it is a valid mountain array.

Recall that arr is a mountain array if and only if:

• 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]
  
  
  
  

Example 1:

Input: arr = [2,1]
Output: false

Example 2:

Input: arr = [3,5,5]
Output: false

Example 3:

Input: arr = [0,3,2,1]
Output: true

Constraints:

• 1 <= arr.length <= 104


• 0 <= arr[i] <= 104