Multigraph?

[cryo75]

is it possible to change the main Dijkstra algorithm to search multigraphs? Most probably yes, but what are the changes required because the edges are added to a HashMap?

[mcourteaux]

You can insert auxiliary nodes yourself, connected by a zero-cost edge.

A -----> B
 \______/

Becomes:

A ---> A1 ---> B
\             /
 \---> A2 ---/

Where the edges from A to A1 and from A to A2 have zero cost. The other edges have the same cost as before.