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Longest Consecutive Sequence - Leetcode 128 - Python

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
class Solution:
    def longestConsecutive(self, n: List[int]) -> int:
        ns = set(n) 
        lgt = 0
        
        for i in n:
            #seq start or not?
            if i-1 not in ns:
                lth = 0
                while i + lth in ns:
                    lth += 1
                lgt = max(lth, lgt)
        return lgt


Explaination :








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