Compute longest increasing subsequence
Company: TikTok
Role: Machine Learning Engineer
Category: Coding & Algorithms
Difficulty: Medium
Interview Round: Onsite
Given an integer array nums, compute the length of a longest strictly increasing subsequence and also output one valid subsequence. Aim for an O(n log n) approach; explain the binary-search (patience sorting) technique, how to reconstruct the subsequence, and analyze time/space complexity. Follow-ups: adapt to non-decreasing subsequences, handle duplicates carefully, and discuss how to count how many LIS exist.
Quick Answer: This question evaluates understanding of sequence algorithms, dynamic programming concepts, and algorithmic optimization for the longest increasing subsequence problem, including subsequence reconstruction and complexity analysis.