128. Longest Consecutive Sequence

class Solution:
    def longestConsecutive(self, nums: List[int]) -> int:
        s = set(nums)
        res = 0
        for n in s:
            if (n - 1) not in s:
                length = 0
                while (n + length) in s:
                    length += 1
                res = max(res, length)
        return res

• T: $O(n)$
• S: $O(n)$