Passage Tracker: Track and Query Entities Passing Through Checkpoints in Order

Problem You are given a sequence of events: {entity_id, checkpoint_id, timestamp}. An entity "completes the passage" if it passes through all required checkpoints in the correct order (by timestamp). Given the list of events and an ordered list of required checkpoints, return all entity IDs that completed the passage, sorted ascending. Example: Follow-ups What is the time complexity of your approach? How would you handle an entity that passes through a checkpoint multiple times? If checkpoints c…