[LeetCode] Valid Mountain Array

🔍  문제

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
• arr[0] < arr[1] < ... < arr[i - 1] < 
• arr[i]arr[i] > arr[i + 1] > ... > arr[arr.length - 1]

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

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

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

 

🖥  실행

1) Answer

class Solution:
    def validMountainArray(self, A):
        i, j, n = 0, len(A) - 1, len(A)
        while i + 1 < n and A[i] < A[i + 1]: i += 1
        while j > 0 and A[j - 1] > A[j]: j -= 1
        return 0 < i == j < n - 1