sk's answer is technically correct. However, my experiences has been that one very rarely has a completely generic graph. Usually, there's additional information about how the graph is built that can remove the NP-completeness from a find_all_cycles() function.

A few items to look for could be:

My criteria for good software:
  1. Does it work?
  2. Can someone else come in, make a change, and be reasonably certain no bugs were introduced?

In reply to Re: Cycle in Directed Graph by dragonchild
in thread Cycle in Directed Graph by artist

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