The Reve's Puzzle
An iPhone Application by Sam and Pui Hin Rhoads
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Details about solving the puzzle and what happens when you do.
Questions and Comments
This is the classic "The Reve's Puzzle" from Henry E. Dudeney's "The Canterbury Puzzles".

When Chaucer's Pilgrims stopped at a wayside tavern, the Reve — a "wily man" according to Chaucer — set up four stools, placed eight cheeses of differing sizes on one of the stools, and challenged the other pilgrims to move them to one of the other stools in the least number of moves. They have to be moved one at a time, and a larger cheese can never be placed on a smaller. After eight cheeses have been successfully moved, the challenge is to move nine. After nine have been moved, the challenge is to move ten. In each case, they have to be moved in the least number of moves possible. When a pilgrim finally moves 21 cheeses in the least number of moves, the Reve will give that pilgrim "a draught of the best that our good host can provide."

 splash
scroll starting after a few start over
This instructions scroll tells the player about the Reve and the puzzle.
When Puzzle Mode begins, this is the first screen the user sees.
This shows what the puzzle looks like after the user has made a few moves.
A Pilgrim can start over at any time.
change number congratulations show me moving
The Lite Version allows a maximum of 15 cheeses. In Practice mode of the Full Version you can choose up to 21.
When a Pilgrim succeeds in moving the cheeses at any level, this "Congratulations" screen appears.
A Pilgrim can ask the Reve to show him or her how to move the cheeses.
After 21 cheeses are moved, you get a "draught from the Reve."
 
NOTES:

In this puzzle, you -- the Pilgrim -- are challenged to move the cheeses from the starting stool to one of the other stools. The goal is to move them in as few moves as possible.

In the Lite version, you:

  • Must move the cheeses one at a time,
  • May not put a larger cheese on top of a smaller one,
  • May take back an inadvertent move but only if you do so immediately,
  • May start over whenever you wish,
  • Can ask the Reve to show you how to move the cheeses,
  • Can choose from 8 through 15 cheeses, and
  • Can see the scroll of instructions at any time.
  
The Full version has two modes, a Practice mode and a Puzzle mode.

In Practice mode, you can do everything you can do in the Lite version plus you can choose from 8 through 21 cheeses.

In Puzzle mode, you:

  • Start with eight cheeses and must move them to another stool in the least number of moves before moving on to nine cheeses, and then 10, etc.,
  • May start over at the beginning of a level whenever you wish, but cannot get to the next level until you succeed at the current level,
  • Cannot ask the Reve to show you how to move the cheeses,
  • Can exit the puzzle at at any point and resume from that point later,
  • Will earn a "draught of the best" when you complete all the levels. At that time you can also add your name to our web page of Pilgrims who have earned a draught from the Reve.

  
Technical Notes:

The question of determining the minimum number of moves required to move n cheeses in The Reve's Puzzle is still open. The "Frame–Stewart Algorithm" — published in 1939 — describes a method of moving the cheeses similar to the one used in this app, but it has not been proven that this method provides a minimum number of moves. By all accounts, this is a very difficult problem of mathematics.

The illustrations and graphics for this app were created by Judy Coppola of Sava Design (www.savadesign.com)

You can visit a web page containing a Java Applet that demonstrates The Reve's Puzzle.

 
Further notes:
  • When the Reve shows a Pilgrim how to solve the puzzle, he does not do it the same way every time. The Reve has different ways of moving the cheeses. We wouldn't want a Pilgrim to depend on just watching the Reve do it in order to learn how.
  • The Lite version and the Full version run in OS 3.0 and higher.
  • When players solve the puzzle (i.e., move 21 cheeses in the minimum number of moves), they will be handed a "draught of the finest" and will have an opportunity to mail their name and the time they took to us. We will post those names and times on an "Honor Role" of successful pilgrims.
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We want to hear from you regarding any suggestions you have for improving the puzzle.

If you have suggestions, please write to us.

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© 2009 / 2010 Sam and Pui Hin Rhoads