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Programming Enigma Puzzles

18 December 2013

Posted by on **From New Scientist #2948, 21st December 2013** [link]

Joe’s problem for Penny this week was to number each triangle of an icosahedron with one of the digits 1 to 5 so that each of the five triangles meeting at a point was numbered differently. Some of the digits in Penny’s solution are shown in the diagram of an icosahedron dissected and laid flat. Six of the digits are covered with the letters ENIGMA. What are those digits?

**New Scientist** has announced that this will be the final *Enigma* puzzle.

I’m a little bit shocked, as I’ve become used to programming solutions to them. Fortunately I’m not quite a third of the way through the archive of all *Enigma* puzzles, so I’ll be able to keep posting classic puzzles for some time.

[enigma1780]

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This puzzle is quite similar to

Enigma 1391(also by Bob Walker), so I took that code and modified it slightly to solve this puzzle. This Python program runs in 33ms.Solution:ENIGMA = 324125.Sadly, a very easy puzzle to solve manually:

Using Jim’s numbering, #18 has to be 4, #1 has to be 1.

#9 must be 1 or 5. Trying #9 = 5, chasing round the vertices quickly leads to a contradiction, so #9=1, and the remaining cells can be filled in by chasing round the vertices.

It’s sad to see Enigma go out with such an easy puzzle. I will miss it, as I have been doing Enigma, and its predecessor Tantalizer since I was at school in the early 1970s.

I will have to do more Project Euler from now on, and of course old Enigmas that Jim puts up.

You’re right – it is very straightforward by hand. A bit of a shame for Enigma to bow out in such a manner. Although it’s been quite a while since we’ve had a really interesting puzzle in the magazine – most of the one’s I’ve been finding fun to solve have been from back issues.

I’ll keep adding “classic” puzzles to the site. I’ll probably put a new one up every other day starting on Saturday.

I am surprised and disappointed to see the New Scientist enigma puzzles go – I hope that the Sunday Times doesn’t drop its teasers in the same way.

As a late commer to the Enigmas I am surprised to see the whole series end in 1780.

Fortunately we have Jim Randell who is spending tremendous time to fill up all the missing enigmas My teaser history goes back to early 1960’s with the Brain Twister of the Observer and The Brain Teaser of the Sunday Times, the former one being stopped in the 300’s with the loss of Dr.Barnard.

Now just as I became so familiar with the Enigmas we have to say bye bye unfortunately and be content with the 1780 enigmas.

Fortunately Jim and Brian are the two volunteers who insistingly and consistingly follow up and let us continue in helping our brains updated day after day if not week after week

Carry on dancing in refreshing our minds.

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