Problem editorial

Longest Turbulent Subarray

MediumSliding WindowArrayGreedySliding Window

Longest Turbulent Subarray: the approach in brief

The problem

Given an integer array arr, a subarray is a contiguous, non-empty portion of the array. A subarray is turbulent when each pair of neighboring values alternates between a strict increase and a strict decrease: the comparisons must follow either > then and so on, or then , , <, so the entire array is turbulent.

Pattern

Longest Turbulent Subarray is a Sliding Window problem, in the Variable Size (Condition-Based) subpattern. The pattern covers fixed-size, variable-size, and character frequency matching window techniques

Approach outline

Examine the direction of each comparison between adjacent values.
When the next comparison has the opposite direction from the previous one, the current turbulent range can be extended.
An equality immediately ends the current turbulent range, while two consecutive comparisons with the same direction require starting a new range from the previous element.

Complexity

The reference solution runs in O(n), where n is arr.size(). time and O(1). space.

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Practise Longest Turbulent Subarray and the problems around it

Longest Turbulent Subarray is a Sliding Window problem, in the Variable Size (Condition-Based) subpattern. Once the approach above makes sense, write it yourself and then work through the neighbouring problems that reuse it.

Longest Turbulent Subarray