WRITE · TRACE · UNDERSTAND
Topological Sort
Release tasks as their final prerequisite is removed
Your experiment
task_order(graph) returns any valid prerequisite-first order, or None for a cycle. graph maps every node to outgoing neighbours; every neighbour is a key.
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What to look for
Indegree counts prerequisites that remain. Removing a ready task reduces the counts of its dependants. If no task is ready but some remain, a cycle blocks the schedule.
Watch your code work
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