def longestConsecutive(nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        # If list empty, return 0
        if not nums:
            return 0
    
        # Create a set for O(n) search
        num_set = set(nums)
        longest_streak = 0

        for num in num_set:
            if num - 1 not in num_set:  # Start of a potential streak
                current_num = num
                current_streak = 1

                while current_num + 1 in num_set:  # Continue the streak
                    current_num += 1
                    current_streak += 1

                longest_streak = max(longest_streak, current_streak)

        return longest_streak



# print(longestConsecutive([100,4,200,1,3,2]))
# print(longestConsecutive([0,3,7,2,5,8,4,6,0,1]))
# print(longestConsecutive([1,3,5,2,4]))
# print(longestConsecutive([9,1,4,7,3,-1,0,5,8,-1,6]))
print(longestConsecutive([1,2,0,1]))