Given an array A of integers, return true if and only if it is a valid mountain array.
Recall that A is a mountain array if and only if:
A.length >= 3- There exists some i with
0 < i < A.length - 1such that:A[0] < A[1] < ... A[i-1] < A[i]A[i] > A[i+1] > ... > A[B.length - 1]
Example 1:
Input: [2,1]
Output: false
Example 2:
Input: [3,5,5]
Output: false
Example 3:
Input: [0,3,2,1]
Output: true
Note:
0 <= A.length <= 100000 <= A[i] <= 10000