941. 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