维护两个字典，一个字典记录某数的前序序列，一个记录后续序列
应该还有优化空间
class Solution(object):
def longestConsecutive(self, nums):
if len(nums)==0:
return 0
up_dict={}
down_dict={}
for num in nums:
if num in up_dict:
continue
if num-1 in up_dict:
up_left=up_dict[num-1][0]
up_dict[num]=[up_left,num]
else:
up_dict[num]=[num,num]
if num+1 in down_dict:
down_right=down_dict[num+1][1]
down_dict[num]=[num,down_right]
else:
down_dict[num]=[num,num]
down_dict[up_dict[num][0]]=[up_dict[num][0],down_dict[num][1]]
up_dict[down_dict[num][1]]=[up_dict[num][0],down_dict[num][1]]
def count_seq(num):
return up_dict[num][1]-up_dict[num][0]+down_dict[num][1]-down_dict[num][0]+1
return max(map(count_seq,nums))
