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] < A[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 <= 10 4 0 <= arr[i] <= 10 4 Solution: class Solution { public boolean validMountainArray(int[] arr) { int n = arr.length, i = 0, j = n - 1; while (i+1 < n && arr[i] < arr[i + 1]) i++; while (j > 0 && arr[j - 1] >