Mountain Array with Java Script

What is Mountain Array?
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]

Examples Of Mountain Arrays.
Example 1:

Input: [2,1]
Output: false
Example 2:

Input: [3,5,5]
Output: false
Example 3:

Input: [0,3,2,1]
Output: true

Solution Approach

It's very easy to keep track of a monotonically increasing or decreasing ordering of elements. You just need to be able to determine the start of the valley in the mountain and from that point onwards, it should be a valley i.e. no mini-hills after that. Use this information in regards to the values in the array and you will be able to come up with a straightforward solution.

so as per above explanation,

• if(A.length > 3){
  let n = A.length;
  let i = 0;

  while(i+1 < n && A[i] < A[i+1]){
      i++;
  }
  
  if(i==0 || i == n-1){
      return false
  }
  
  while(i+1 < n && A[i] > A[i+1] ){
      i++;
  }
  return i == n-1;
  

  }
  else{
  return false
  }
  *
  -> here A is Array.