BinarySearch 0653 Longest Strictly Increasing Then Decreasing Sublist

Problem statement

https://binarysearch.com/problems/Longest-Strictly-Increasing-Then-Decreasing-Sublist/

Solution

Equal to Leetcode 0845. Longest Mountain in Array.

Complexity

It is O(n) for time and space.

Code

class Solution:
    def solve(self, A):
        n, max_len = len(A), 0
        state, length = 0, 1
        for i in range(n-1):
            if state in [0, 1] and A[i+1] > A[i]:
                state, length = 1, length + 1
            elif state == 2 and A[i+1] > A[i]:
                state, length = 1, 2
            elif state in [1, 2] and A[i+1] < A[i]:
                state, length = 2, length + 1
                max_len = max(length, max_len)
            else:
                state, length = 0, 1
                
        return max_len