Day046 - 128. Longest Consecutive Sequence

128. Longest Consecutive Sequence

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

내 풀이

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

        # The Longest Consecutive Elements Sequence
        lces = 0

        for i in nums:
            if i-1 not in nums_set:

                add_num = 1
                temp_lces = 1

                while (i+add_num) in nums_set:
                    temp_lces += 1
                    add_num += 1

                lces = max(lces, temp_lces)

        return lces

# Time Complexity : \(O(N)\)