FindCycle

A cycle among the nodes and what their successors reach, its nodes in the order they lead to each other, each once, or Null when there's none. It's the first that depth-first search meets, going from the nodes given in their order: a node that's its own successor is a cycle of one.

Examples

Local leads = {"a": ["b"], "b": ["c"], "c": ["a"]}
Expect(FindCycle(["a"], Function(node: String) => leads[node]) == ["a", "b", "c"])
Expect(TopologicalSort(["a"], Function(node: String) => leads[node]) == Null)