Code Room
CodingMedium
Question
Return the length of the longest common subsequence of strings a and b. A subsequence keeps relative order but need not be contiguous; for example "abcde" and "ace" have LCS "ace" of length 3. Either string may be empty (answer 0). Strings can be up to ~1000 characters; an O(len(a)*len(b)) DP is expected, with O(min(len)) space achievable.
Implement
lcs_length(a: str, b: str) → intExamples
in
["abcde","ace"]out3What a strong answer looks like
State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.
Learn the concepts
Vibe coding: describe the solution in plain language (or narrate it) and the coach grades your approach. Generating runnable code from your description is coming next.
Run or narrate your approach, then ask the coach.