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top_sort(+Graph, -Sorted)

Finds a topological ordering of the graph if one exists
Graph
a graph structure
Sorted
a list of integer node numbers

Description

Finds a topological ordering of the graph, i.e. an ordering of the nodes such that all edges go from earlier to later nodes. Such an ordering exists if and only if the graph is acyclic. If the graph is cyclic, the predicate fails.

In general, the ordering is not unique, an arbitrary one is computed. The complexity is O(Nnodes + Nedges).

Modes and Determinism

Fail Conditions

No topological ordering exists, i.e. the graph is cyclic

See Also

graph_is_acyclic / 1, graph_cycles / 2