Harmonious Subsequence

Problem

Given an array of integers nums, find the length of the longest harmonious subsequence where the difference between the maximum and minimum numbers is exactly one. A subsequence is a sequence that can be derived from another sequence by deleting some or no elements without changing the order of the remaining elements.

Examples

findLHS([2,4,3,3,6,3,4,8])
// returns 5
// The longest harmonious subsequence is [4,3,3,3,4]

findLHS([2,3,4,5])
// returns 2
// The harmonious subsequences could
// be [2,3] or [3,4], each of length 2

findLHS([2,2,2,2])
// returns 0
// There's no harmonious subsequence as
// the difference between the maximum and minimum is not one