594. Longest Harmonious Subsequence（easy）

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

Now, given an integer array, you need to find the length of its longest harmonious subsequence among all its possible subsequences.

Example 1:

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

Note: The length of the input array will not exceed 20,000.

 使用hashmap存储每个数出现的次数

相减为1说明只能是相邻2个数组成的串，而每个数可能存在左右2个相邻数字，这时就要比较哪个比较大

class Solution:
    def findLHS(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
    
        count = collections.Counter(nums)
        ll = 0;lr=0;lf=0;
        setnum = set(nums)
        for key,val in count.items():
            l = val
            if (key + 1) in setnum:
                lr = l + count[key+1]
            if (key - 1) in setnum:
                lf = l +  count[key-1]
            l = max(lf,lr)
            ll = max(ll,l)         
        return ll