# Valid Mountain Array

Updated: Mar 25, 2021

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]

**Example 1:**

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

**Example 2:**

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

**Example 3:**

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

**Constraints:**

1 <= arr.length <= 104

0 <= arr[i] <= 104

**Solution:**

```
class Solution {
public boolean validMountainArray(int[] arr) {
int left = 0, right = arr.length-1;
if(arr.length<3) return false;
while(left<right && arr[left]<arr[left+1])
left++;
while(right>=1 && arr[right]<arr[right-1])
right--;
if(right!=0 && left!=arr.length-1 && left==right) return true;
return false;
}
}
```