2765 - Longest Alternating Subarray.

Easy

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

• m is greater than 1.

• <code>s₁ = s₀ + 1</code>.

• The 0-indexed subarray s looks like <code>s₀, s₁, s₀, s₁,...,s_{(m-1) % 2}</code>. In other words, <code>s₁ - s₀ = 1</code>, <code>s₂ - s₁ = -1</code>, <code>s₃ - s₂ = 1</code>, <code>s₄ - s₃ = -1</code>, and so on up to <code>sm - 1 - sm - 2 = (-1)^m</code>.

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 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

• <code>1 <= numsi<= 10⁴</code>