594. Longest Harmonious Subsequence

class Solution(object):
    def findLHS(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        cnt={}
        for num in nums:
            if num not in cnt:
                cnt[num]=1
            else:
                cnt[num]+=1
        res=0
        for k in cnt.keys():
            if k-1 in cnt:
                res=max(cnt[k-1]+cnt[k],res)
            if k+1 in cnt:
                res=max(cnt[k+1]+cnt[k],res)

        return res