rustworkx.digraph_dijkstra_search

digraph_dijkstra_search(graph, source=None, weight_fn=None, visitor=None)

Dijkstra traversal of a directed graph.

The pseudo-code for the Dijkstra algorithm is listed below, with the annotated event points, for which the given visitor object will be called with the appropriate method.

DIJKSTRA(G, source, weight)
  for each vertex u in V
      d[u] := infinity
      p[u] := u
  end for
  d[source] := 0
  INSERT(Q, source)
  while (Q != Ø)
      u := EXTRACT-MIN(Q)                         discover vertex u
      for each vertex v in Adj[u]                 examine edge (u,v)
          if (weight[(u,v)] + d[u] < d[v])        edge (u,v) relaxed
              d[v] := weight[(u,v)] + d[u]
              p[v] := u
              DECREASE-KEY(Q, v)
          else                                    edge (u,v) not relaxed
              ...
          if (d[v] was originally infinity)
              INSERT(Q, v)
      end for                                     finish vertex u
  end while

If an exception is raised inside the callback function, the graph traversal will be stopped immediately. You can exploit this to exit early by raising a StopSearch exception, in which case the search function will return but without raising back the exception. You can also prune part of the search tree by raising PruneSearch.

Note

Graph can not be mutated while traversing.

Parameters:

• graph (PyDiGraph) – The graph to be used.

• source (List[int]) – An optional list of node indices to use as the starting nodes for the dijkstra search. If this is not specified then a source will be chosen arbitrarly and repeated until all components of the graph are searched.

• weight_fn – An optional weight function for an edge. It will accept a single argument, the edge’s weight object and will return a float which will be used to represent the weight/cost of the edge. If not specified, a default value of cost 1.0 will be used for each edge.

• visitor – A visitor object that is invoked at the event points inside the algorithm. This should be a subclass of DijkstraVisitor. This has a default value of None as a backwards compatibility artifact (to preserve argument ordering from an earlier version) but it is a required argument and will raise a TypeError if not specified.