leetcode @python 128. Longest Consecutive Sequence

题目链接

https://leetcode.com/problems/longest-consecutive-sequence/

题目原文

Given an unsorted array of integers, find the length of the longest consecutive elements sequence.

For example,

Given

[100, 4, 200, 1, 3, 2]

,

The longest consecutive elements sequence is [

1, 2, 3, 4]

. Return its length:

4

.

Your algorithm should run in O(n) complexity.

题目大意

给定一个序列，返回最长的连续子序列

解题思路

依次遍历序列中的数，使用栈将数和与此数相连的数放进栈（如果这些数在序列中出现），返回栈的最大长度

代码

class Solution(object):
def longestConsecutive(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
nums = set(nums)
res = 0
while nums:
stack = [next(iter(nums))]
tmp = 0
while stack:
tmp += 1
curr = stack.pop()
nums.discard(curr)
if curr - 1 in nums:
stack.append(curr - 1)
if curr + 1 in nums:
stack.append(curr + 1)
res = max(res, tmp)
return res