Longest Alternating Subarray - Video Solutions

EasyArrayEnumeration

Maximum Alternating Subsequence Sum - Dynamic Programming - Leetcode 1911 - Python

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Longest Alternating Subarray - Video Solution

Watch 10 video solutions for Longest Alternating Subarray, a easy level problem involving Array, Enumeration. This walkthrough by NeetCode has 28,064 views views. Want to try solving it yourself? Practice on FleetCode or read the detailed text solution.

Problem Statement

You are given a 0-indexed integer array nums. A subarray s of length m is called alternating if:

m is greater than 1.
s₁ = s₀ + 1.
The 0-indexed subarray s looks like [s₀, s₁, s₀, s₁,...,s_{(m-1) % 2}]. In other words, s₁ - s₀ = 1, s₂ - s₁ = -1, s₃ - s₂ = 1, s₄ - s₃ = -1, and so on up to s[m - 1] - s[m - 2] = (-1)^m.

Return the maximum length of all alternating subarrays present in nums or -1 if no such subarray exists.

A subarray is a contiguous non-empty sequence of elements within an array.

Example 1:

Input: nums = [2,3,4,3,4]

Output: 4

Explanation:

The alternating subarrays are [2, 3], [3,4], [3,4,3], and [3,4,3,4]. The longest of these is [3,4,3,4], which is of length 4.

Example 2:

Input: nums = [4,5,6]

Output: 2

Explanation:

[4,5] and [5,6] are the only two alternating subarrays. They are both of length 2.

Constraints:

2 <= nums.length <= 100
1 <= nums[i] <= 10⁴

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