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24th April 2005


Brian Grainger

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This article discusses the craze for pencil puzzles and the use of computers for creating and solving them. I want to discuss in particular the latest craze for Sudoku.

A pencil puzzle is, not surprisingly, a puzzle where all you need to solve it is a pencil (and a brain!). I guess the first pencil puzzle that most of us come into contact with is the crossword. You only need to look at the newspapers and puzzle magazines to see that crosswords now come in a variety of forms, not just the clues and answer format.

In recent years puzzle magazines have sprung up to provide other types of pencil puzzle, such as the Wordsearch. It makes you wonder why there are so many puzzle magazines. Perhaps we all have too much free time to fritter away now!

Then, of course, we have the longest running quiz show on television, Countdown. This provides a word making puzzle, a numbers puzzle and an anagram puzzle. You may not think of these as pencil puzzles, but they are. Unless you do them in your head, all that is needed to solve them is a pencil and paper.

It is interesting that in all these examples the word puzzle predominates. Only the Countdown numbers game steers away from this trend. Now, think what it would be like to live in Japan! Japanese writing is made up of symbols more like pictures than our alphabet. Consequently, word puzzles have not caught on much in Japan. However, that does not mean that the Japanese do not have a desire for puzzle making. It is just that their pencil puzzles are based on shapes and/or numbers, rather than words.

I guess the first Japanese pencil puzzle I got interested in was the Nonogram. Curiously, this has a link with ICPUG, because the Nonogram was popularised around the world by James Dalgety, an ICPUGSE member. The Nonogram had an unusual birth. In the late 1980s Non Ishida won first prize in a Window Art competition. The competitors had to produce a picture by lighting up the appropriate windows in a skyscraper building! Not only did Non Ishida win but she was a puzzle enthusiast. She devised a puzzle based on the idea of filling in squares on a rectangular grid to create a picture. The filled in squares were the paper equivalent of the windows being lit in the skyscraper. For the puzzle, each row and column is clued with how many neighbouring squares are filled in. A clue such as 5.7 means that there are 5 neighbouring filled in squares (not necessarily at the beginning of the line), followed by 1 or more unfilled squares, followed by 7 filled in squares (not necessarily at the end of the line). Using the clues for each row and column the puzzle solver has to reconstruct the picture.

Here is an example of a completed Nonogram, originally called 'Time' - I have added the colour for effect! The original 'Time' puzzle is copyright Sunday Telegraph & Aenigma Design

James Dalgety is a collector of puzzles and runs the Puzzle Museum web site. Non Ishida showed James her idea and he named them Nonograms in recognition of their inventor. Bringing them to England, they were published in 'The Sunday Telegraph' and that is where I came across them. Since then they have been renamed Griddlers, after Non Ishida wanted to use the name of Nonograms in Japan and the Sunday Telegraph wanted their own exclusive name. I have spent many a 'spare' moment solving them and have a few books of the puzzles waiting for when I retire!

Curiously, I have never been able to find a computer program which solves Nonograms. These puzzles are horribly difficult to create. While it is simple to draw a picture on a grid and then clue the puzzle, it may not be possible to use logic to draw the picture from the clues! James, apparently, uses a program to check if a puzzle is solvable, but no details of the program have ever been released. James also tells me that many programs and applets have been written to both play and solve Nonograms. I just haven't found them yet!

You can find out more of the history of Nonograms/Griddlers at:

More on the Nonogram name is at:

If we move forward in time, to earlier this year, the Daily Telegraph started publishing a puzzle called Sudoku. This also came from Japan and, being based on numbers, instantly aroused my curiosity. After a little research I found the puzzle was originally published in the UK in 'The Times' newspaper in November 2004 and has proved stunningly popular. Considering the number of references to Sudoku already on the web, I think this is an understatement.

The Sudoku puzzle consists of a grid of 81 squares (9 x 9), split into 9, 3 x 3 boxes. Each row, column and box must contain ALL the numbers 1 to 9. You are given some numbers filled in to start with and the solver has to fill in the rest.

Here is an example of a Sudoku puzzle and its solution.

Now, the Sudoku puzzle can sometimes be quite easy to solve and, at other times, diabolical. The Daily Telegraph grade their puzzles, getting progressively more difficult through the week! I warn you that these puzzles are extremely addictive.

The nice thing about Sudoku puzzles is that computer programs can be written to create them and to solve them. I used my favourite to create the above example. I find it amusing that the Times newspaper puzzle is set by an author who has the web site www.sudoku.co.uk and the Daily Telegraph puzzle is set by an author who has the web site www.sudoku.org.uk. The first of these web sites is trying to sell a computer program for cash. The latter is purely for fun and includes an archive of puzzles to date and helpful hints on how to solve Sudoku. It also hosts a forum for solvers.

As I said previously, there are lots of references to Sudoku on the web and it does not take long to find a variety of programs free of charge.

My favourite is Mark Huckvale's Sudoku creator/solver. It can be found at:


Apart from being the only program to be able to create puzzles I have found, it is dead easy to use. No keyboarding is required. Being written in Javascript, it will work in any suitable browser, in Linux as well as Windows and presumably on a Mac.

Another Javascript program can be found at:


This program is unique in that it will explain how the solution is found. However, it will not solve the more difficult problems.

A solver that uses Excel can be found at:


Finally, there is a program that runs as a Windows executable.


If this article has whet your appetite for pencil puzzles a look at the following Japanese web sites, (written in English), will provide some different puzzle ideas and examples to solve.


Have a good time puzzling, but do not get too addicted. Make sure to spare enough time to have a look at the ICPUG web site occasionally!

Update 13/05/2005

When James Dalgety made some comments on the original version of this article, which have been incorporated, he finished his e-mail with the salutation, "Happy Metagrobologising". I did not know what it meant at the time! I have since been told that Metagrobologising is the technical term for solving puzzles.

Update 16/06/2005

Caroline Begbie writes to tell me that, in Australia, Nonograms are known as Tsunami. She also mentioned a web site:

This website contains many online tools for creating, solving and submitting for upload Tsunami puzzles. There is also a program to download that allows you the same functionality offline. However, I am not sure whether it is freeware, shareware or commercial software.

The other interesting thing about this site is that it introduces Nonograms in colour!

Encouraged by Caroline's e-mail I did a new search for Nonograms and found some programs that would solve them. Curiously, the major site seems to have programs to run under the Risc OS and nothing more. However, I have found a program written in Java and there are some online solvers. In all of them providing the input data is a bit tedious. I would not recommend any of them as the definitive creator or solver as yet.