Longest Consecutive Sequence · Interview Problem

Leetcode

longest-consecutive-sequence

Medium

Arrays

Union Find

Hash Table

Longest Consecutive Sequence

Find the length of the longest consecutive elements sequence in an unsorted array of integers.

Acceptance 50%

Problem Statement

Core description from the backend problem record.

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.

An array of integers nums.

An integer representing the length of the longest consecutive sequence.

0 <= nums.length <= 10^5 -10^9 <= nums[i] <= 10^9

Examples

Sample cases returned by the problem API.

Example 1

Input

[100, 4, 200, 1, 3, 2]

Output

Explanation

The longest consecutive sequence is [1, 2, 3, 4], so the output is 4.

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