Problem

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 - 1 such 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 <= 10000

0 <= A[i] <= 10000

Pre analysis

This is one of most complex-simple-perplex kinda problem when it comes to test cases, it only defines what is correct, but few test cases fail because nothing explicit was mentioned about other stuff. Will take greedy approach to this problem