128. 最长连续序列

class Solution(object):
    def longestConsecutive(self, num):
        """
        :type nums: List[int]
        :rtype: int
        """
        if num is None or len(num) == 0:
            return 0
        m = {}
        res = 0
        for i in num:
            if i not in m:
                l = 0
                r = 0
                if i - 1 in m:
                    l = m[i - 1]
                if i + 1 in m:
                    r = m[i + 1]
                m[i] = 1 + r + l
                m[i + r] = 1 + r + l
                m[i - l] = 1 + r + l
                res = max(res, m[i])
        return res