Problem context and objectives
Mission briefing
Expedition navigator · Safe camps and hazards form a connected world map
Find a valid route while marking every place already explored: Course Order.
Without visited state, the party loops forever or revisits expensive terrain.
How you win
- 1Recognize when Kahn topological ordering matches the clues
- 2Keep this true after every move: the queue contains exactly the unplaced courses whose prerequisites have all been placed
- 3Reach the result within O(V + E) time and space
Rules and pressure
- Target cost: O(V + E) time and space
- State rule: the queue contains exactly the unplaced courses whose prerequisites have all been placed
New words in this mission
Open a term for a plain-language explanation.durable queue+
A waiting line that keeps work until a consumer finishes it. It absorbs bursts and lets failed work be retried.
Lesson 1 of 3
Indegree is the number of unfinished prerequisite locks. Only a zero-lock course may enter the ready queue.
Your call · Course 3 still has one lock after placing course 1. Is course 3 ready?