0128-longest-consecutive-sequence.py

from typing import List


class Solution:
    def longestConsecutive(self, nums: List[int]) -> int:
        longestStreak = 0
        numSet = set(nums)

        for num in nums:
            if num - 1 not in numSet:
                currentNum = num
                currentStreak = 1

                while currentNum + 1 in numSet:
                    currentNum += 1
                    currentStreak += 1

                longestStreak = max(longestStreak, currentStreak)

        return longestStreak