Section 1Understand Problem
Section 01
Understand the problem
Restate the problem precisely. Interviewers reward candidates who pause, define the contract, and name the guarantees before coding.
Problem statement
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
nums = [100, 4, 200, 1, 3, 2] → 4
Constraints
0 ≤ nums.length ≤ 10⁵ · −10⁹ ≤ nums[i] ≤ 10⁹
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