594.LongestHarmoniousSubsequence(Counter).py

'''
    We define a harmonious array as an array where the 
    difference between its maximum value and its minimum 
    value is exactly 1.

    Given an integer array nums, return the length of its 
    longest harmonious subsequence among all its possible 
    subsequences.

    A subsequence of array is a sequence that can be derived 
    from the array by deleting some or no elements without 
    changing the order of the remaining elements.

    Example:
    Input: nums = [1,3,2,2,5,2,3,7]
    Output: 5
    Explanation: The longest harmonious subsequence is 
                 [3,2,2,2,3].

    Example:
    Input: nums = [1,2,3,4]
    Output: 2

    Example:
    Input: nums = [1,1,1,1]
    Output: 0

    Constraints:
        - 1 <= nums.length <= 2 * 10^4
        - -10^9 <= nums[i] <= 10^9
'''
#Difficulty: Easy
#206 / 206 test cases passed.
#Runtime: 304 ms
#Memory Usage: 15.8 MB

#Runtime: 304 ms, faster than 71.28% of Python3 online submissions for Longest Harmonious Subsequence.
#Memory Usage: 15.8 MB, less than 93.69% of Python3 online submissions for Longest Harmonious Subsequence.

from collections import Counter

class Solution:
    def findLHS(self, nums: List[int]) -> int:
        numbers = Counter(nums)
        result = 0
        for num, count in numbers.items():
            if num+1 in numbers:
                result = max(result, numbers[num] + numbers[num+1])
        return result