Description
Given an unsorted array of integers nums, return the length of the longest consecutive elements sequence.
You must write an algorithm that runs in O(n) time.
Example 1:
Input: nums = [100,4,200,1,3,2]
Output: 4
Explanation: The longest consecutive elements sequence is [1, 2, 3, 4]. Therefore its length is 4.
Example 2:
Input: nums = [0,3,7,2,5,8,4,6,0,1] Output: 9
Constraints:
0 <= nums.length <= 105-109 <= nums[i] <= 109
Solution
Python3
class Solution:
def longestConsecutive(self, nums: List[int]) -> int:
s = set(nums)
res = 0
while s:
first = last = s.pop()
while first - 1 in s:
s.remove(first - 1)
first -= 1
while last + 1 in s:
s.remove(last + 1)
last += 1
res = max(res, last - first + 1)
return res