Longest Turbulent Subarray https://leetcode.com/problems/longest-turbulent-subarray/

turbulent.py

class Solution:
    def maxTurbulenceSize(self, arr: List[int]) -> int:
        # O(n)
        max_length = 1
        is_greater = None
        cur_length = 1

        for i in range(len(arr) - 1):
            # Compare the current and next array values.
            s0 = arr[i]
            s1 = arr[i+1]

            # Initialize condition or flip it.
            is_greater = (not is_greater) if is_greater != None else s0 > s1

            if (is_greater and s0 > s1) or (not is_greater and s0 < s1):
                cur_length += 1
            else:
                # Not valid. Check if we've found a longest subarray up to this point.
                max_length = max(cur_length, max_length)
                cur_length = 2 if s0 != s1 else 1
                is_greater = not is_greater

        return max(cur_length, max_length)

znote.txt

978. Longest Turbulent Subarray
Solved
Medium
Topics
Companies
Given an integer array arr, return the length of a maximum size turbulent subarray of arr.

A subarray is turbulent if the comparison sign flips between each adjacent pair of elements in the subarray.

More formally, a subarray [arr[i], arr[i + 1], ..., arr[j]] of arr is said to be turbulent if and only if:

For i <= k < j:
arr[k] > arr[k + 1] when k is odd, and
arr[k] < arr[k + 1] when k is even.
Or, for i <= k < j:
arr[k] > arr[k + 1] when k is even, and
arr[k] < arr[k + 1] when k is odd.
 

Example 1:

Input: arr = [9,4,2,10,7,8,8,1,9]
Output: 5
Explanation: arr[1] > arr[2] < arr[3] > arr[4] < arr[5]
Example 2:

Input: arr = [4,8,12,16]
Output: 2
Example 3:

Input: arr = [100]
Output: 1