Sign in

[Java][Leetcode] Array — Valid Mountain Array #941

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[A.length - 1]

Example 1:

Example 2:

Example 3:

Note:

  1. 0 <= A.length <= 10000
  2. 0 <= A[i] <= 10000

I set two flags to memorize that is array elements are Increasing or Decreasing ever. Track of increasing or decreasing ordering of elements. Determine the start of the valley in the mountain and from that point onwards.