0941 - Valid Mountain Array

0941 - Valid Mountain Array

Given an array of integers arr, return true if and only if it is a valid mountain array.

Recall that arr is a mountain array if and only if:

• arr.length >= 3

• There exists some i with 0 < i < arr.length - 1 such that:

• • arr[0] < arr[1] < ... < arr[i - 1] < arr[i]

• • arr[i] > arr[i + 1] > ... > arr[arr.length - 1]

Examples

Input: arr = [2,1] Output: false

Input: arr = [3,5,5] Output: false

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

Constraints

• 1 <= arr.length <= 104

• 0 <= arr[i] <= 104

Java Solution

class Solution {
    public boolean validMountainArray(int[] arr) {
        if(arr.length < 3) return false;
        int index = 0;
        
        while(index < arr.length - 1 && arr[index] < arr[index+1]) index++;
        if(index == 0 || index == arr.length - 1) return false;
        
        while(index + 1 < arr.length && arr[index] > arr[index + 1]) index++;
        
        return index == arr.length-1;
    }
}