leetcode/0128_longest-consecutive-sequence/python3/solution.py

# Time: O(N)
# Space: O(N)
class Solution:
    def longestConsecutive(self, nums: List[int]) -> int:
        visited = {}
        
        for _, num in enumerate(nums):
            visited[num] = False
            
        maxl = 0
        
        for _, num in enumerate(nums):
            if visited[num]:
                continue
            
            l = 1
            prev = num - 1
            while prev in visited:
                visited[prev] = True
                l += 1
                prev -= 1
            
            next = num + 1
            while next in visited:
                visited[next] = True
                l += 1
                next += 1
            
            maxl = max(maxl, l)
        
        return maxl