Valid Mountain Array
Updated Feb 24, 2026
Problem
Return true if arr strictly increases then strictly decreases.
Constraints
1 <= arr.length <= 10^4
Examples
Example 1
Input:
{"arr": [0, 3, 2, 1]}
Output:
true
Function Signature
def validMountainArray(self, arr: list[int]) -> bool
How to Submit
Implement a Solution class with a validMountainArray method.
Your method will be called with the input parameters and should return the answer.