[LeetCode] 941. Valid Mountain Array

 Problem : https://leetcode.com/problems/valid-mountain-array/

Simulate the validation process.

class Solution {
    public boolean validMountainArray(int[] arr) {
        if (arr.length < 3) return false;
        
        int i = 0;
        
        // is strictly increasing
        while (i + 1 < arr.length && arr[i] < arr[i+1]) {
            i += 1;
        }
        
        if (i == 0 || i + 1 == arr.length) return false;
      
        // is strictly decreasing
        while (i + 1 < arr.length && arr[i] > arr[i+1] ) {
            i += 1;
        }
        
        return i+1 == arr.length;
    }
}