A GraphViz solution to a D&D reindeer puzzle from HN.

reindeer-riddle.md

The original riddle posted on HN.

Official solution: Dancer -> Donder -> Comet -> Vixen -> Blitzen -> Dasher -> Rudolph -> Cupid -> Prancer

My solution's demo link

Solution code:

digraph {
  rankdir=LR;
  -- Vixen should be behind Rudolph, Prancer and Dasher, whilst Vixen should be in front of Dancer and Comet.
  Vixen -> Rudolph;
  Vixen -> Prancer;
  Vixen -> Dasher;
  Dancer -> Vixen;
  Comet -> Vixen;
  -- Dancer should be behind Donder, Blitzen and Rudolph.
  Dancer -> Donder;
  Dancer -> Blizten;
  Dancer -> Rudolph;
  -- Comet should be behind Cupid, Prancer and Rudolph.
  Comet -> Cupid;
  Comet -> Prancer;
  Comet -> Rudolph;
  -- Donder should be behind Comet, Vixen, Dasher, Prancer and Cupid.
  Donder -> Comet;
  Donder -> Vixen;
  Donder -> Dasher;
  Donder -> Prancer;
  Donder -> Cupid;
  -- Cupid should be in front of Comet, Blitzen, Vixen, Dancer and Rudolph.
  Comet -> Cupid;
  Blizten -> Cupid;
  Vixen -> Cupid;
  Dancer -> Cupid;
  Rudolph -> Cupid;
  -- Prancer should be in front of Blitzen, Donder and Cupid.
  Blizten -> Prancer;
  Donder -> Prancer;
  Cupid -> Prancer;
  -- Blitzen should be behind Cupid but in front of Dancer, Vixen and Donder.
  Blizten -> Cupid;
  Dancer -> Blizten;
  Vixen -> Blizten;
  Donder -> Blizten;
  -- Rudolph should be behind Prancer but in front of Dasher, Dancer and Donder.
  Rudolph -> Prancer;
  Dasher -> Rudolph;
  Dancer -> Rudolph;
  Donder -> Rudolph;
  -- Finally, Dasher should be behind Prancer but in front of Blitzen, Dancer and Vixen.
  Dasher -> Prancer;
  Blizten -> Dasher;
  Dancer -> Dasher;
  Vixen -> Dasher;
}

You could simplify the solution graph by piping it through tred, i.e. do a transitive reduction...

Oh cool, I hadn't heard of tred before, thanks. I didn't run GraphViz locally though—just via the web so while you're right that it'd make the solution simpler, it makes "deployment" (so to speak) more complex.