Longest Consecutive Sequence

arrayhash tableunion-find

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
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

Example 3

Input: nums = [1,0,1,2]
Output: 3

0 <= nums.length <= 10 ^5

-10 ^9 <= nums[i] <= 10 ^9

🤔

Medium

Difficulty

Topic Info

ModuleDSA

CategoryArray

Sub-topicHash Table