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978. Longest Turbulent Subarray

Difficulty Topics

Description

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

 

Constraints:

  • 1 <= arr.length <= 4 * 104
  • 0 <= arr[i] <= 109

Solution

longest-turbulent-subarray.py
class Solution:
    def maxTurbulenceSize(self, arr: List[int]) -> int:
        n = len(arr)
        res = curr = 0

        for i in range(n):
            if i >= 2 and ((arr[i - 2] > arr[i - 1] < arr[i]) or (arr[i - 2] < arr[i - 1] > arr[i])):
                curr += 1
            elif i >= 1 and arr[i - 1] != arr[i]:
                curr = 2
            else:
                curr = 1

            res = max(res, curr)

        return res