Leetcode 128. Longest Consecutive Sequence (Python)

Given an unsorted array of integers nums, return the length of the longest consecutive elements sequence.

You must write an algorithm that runs in O(n) time.

Example 1:

Input: nums = [100,4,200,1,3,2]
Output: 4
Explanation: The longest consecutive elements sequence is [1, 2, 3, 4]. Therefore its length is 4.

Example 2:

Input: nums = [0,3,7,2,5,8,4,6,0,1]
Output: 9

Constraints:

• 0 <= nums.length <= 105
• -109 <= nums[i] <= 109

class Solution(object):
    def longestConsecutive(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        nums = list(set(nums))
        nums.sort()
        if nums == []:
            return 0
        
        if len(nums) == 2 and nums[1] - nums[0] == 1:
            return 2
        elif len(nums) == 2 and nums[1] - nums[0] != 1:
            return 1
        
        if len(nums) == 1:
            return 1
        
        lst = []
        for i in range(len(nums)-1):
            cha = nums[i+1] - nums[i]
            lst.append(cha)
            
        print(nums)
        print(lst)
            
        lst1 = []
        temp = 0
        for j in lst:
            if j == 1:
                temp += 1
                lst1.append(temp)
            else:
                temp = 0
                
        if lst1 == []:
            return 1
        
        return max(lst1) + 1