Problem context and objectives
Mission briefing
Live-ops game engineer · A multiplayer arena is reporting bursts of lag
Find the smallest or strongest contiguous time window: The Unique Lightpath.
Scanning the entire history after every event cannot keep up with live players.
How you win
- 1Recognize when Last-seen frequency window matches the clues
- 2Keep this true after every move: every character inside the live window is unique
- 3Reach the result within O(n)
Rules and pressure
- Target cost: O(n)
- State rule: every character inside the live window is unique
Lesson 1 of 3
Remember each glyph's last position. If its earlier copy is still inside the live trail, jump left just beyond it.
Your call · abc receives another a. Where should left jump?