leetcode 128. Longest Consecutive Sequence

class Solution:
    def longestConsecutive(self, nums: List[int]) -> int:
        nums=list(set(nums))
        nums.sort()
        ans=1
        start=1
        for i in range(1,len(nums)):
            if nums[i]-1 == nums[i-1] :
                start+=1
            else :
                ans=max(ans,start)
                start=1
        ans=max(ans,start)
        if len(nums) ==0 :
            ans=0
        return ans