All 6 entries tagged Sudoku

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December 11, 2009

Friday Puzzles #27

Apologies for the delay, I’m sure you all know what things are like as Christmas approaches.

This week, I’ve decided to write a sudoku. After much experimentation with a certain pattern, I’ve grudgingly had to modify things a little in order to avoid either an impossibly (well not quite impossible, by definition, but you know what I mean) difficult puzzle, or a puzzle with multiple solutions. Still, after a quick check with scanraid (which actually appears to have renamed itself “SudokuWiki” which IMO is more than a little pretentious and misleading in its current form) to get an indication of the difficulty, it would appear to be on par with a Times fiendish puzzle and so I get the satisfaction of writing a puzzle which ought not be solvable in quite so much of a hurry as my previous efforts.

Another point of discussion is that as sudoku puzzles increase in difficulty, the more guessing strategies become useful if you want to go for the quickest times. This is where hand-made puzzles can come in – the cunning trick to crack the puzzle ought to be more obvious to the solver than a standard puzzle out of the generator. This is purely because the human eye is better equipped to pick up subtle clues as suggested by the aesthetics of the puzzle because said aesthetics are a big deal for the author of sudoku puzzles by hand. I’ve left that statement intentionally a little vague, because I hope dearest reader, that you’ll see exactly what I mean whilst solving. Enjoy!

#032 Sudoku – rated hard

All puzzles © Tom Collyer 2009


November 20, 2009

Friday Puzzles #24

In the last couple of days, I’ve engaged in a discussion on Thomas Snyder’s blog about the subtleties, nuances and differences between computer-generated sudoku puzzles, and human created puzzles; in particular if there is a line to be drawn, and just how blurred it might be. If you are interested in that sort of thing, some fascinating things are discussed.

Inevitably, I’ve taken a bit of inspiration from that and I’ve made a sudoku puzzle for this week, all by myself! I’ve used a slightly infamous pattern – which if a computer generator was left to its own devices to find would probably give you something turned up to 11 (again) – but perhaps said computer generator could be programmed to a certain set of rules, and perhaps it could put out a puzzle with a similar difficulty level without taking an hour and a half to do so.

Either way, I’d like to think that you, dearest reader and most loyal of solvers, might feel something of a human touch in this puzzle. Enjoy.

#029 Sudoku – rated easy

All puzzles © Tom Collyer 2009


October 02, 2009

Friday Puzzles #16

You may have heard I became a two-time national champion last weekend. Haha – that’s all well and good because though I’m fairly proficient at solving reasonably difficult sudoku, I’m a bit crap at writing them. Nevertheless, there was no way that I wasn’t going to write a sudoku this week, and here it is.

I expect some rapid times – I haven’t gone at it myself but I suspect that quickest possible is closer to 1 minute than it is to 2.

And with regards to the championships? Expect a nice long and boring write-up of that soon! :)

#021 Sudoku – rated easy

All puzzles © Tom Collyer 2009


September 25, 2009

I Will – a.k.a. Friday Puzzles #15

This week’s entry in my Friday Puzzles series gets its own proper Radiohead-song-title because I’ve managed to go off on one and explored a few deeper avenues than I would have normally done.

Last week’s introduction to the Heyawake puzzle I have decided was a bit hard as an introduction to the puzzle – although I’m now confident it wasn’t totally unfair having had this feedback from one of the best nikoli.com solvers out there:

I liked it! The start was simple enough, and then you made some medium-level deductions to get some big sets of blocks, etc. I’d say the grand finale (I felt pretty sure there were two solutions or more…no, I was wrong) isn’t as bad as you claim. It probably shouldn’t be someone’s first Heyawake, but it’s not the pinnacle of difficulty. It’s a harder medium, how’s that for a/n non-/answer?

On the other hand, I’ve been having a little think about the nature of difficulty and the nature elegance within a puzzle. I think it’s fair to say that by no means are the two are correlated – see this entry for two examples of sudoku too hard to be elegant – well elegant for the pen and pencil solver anyway. To labour the point a little bit more, here is an example of a puzzle which is INSANELY difficult. If you solve it, the only logical deduction is that you used a computer:


I found that puzzle after routing around a forum discussion of the hardest sudoku puzzles, it has been given the slightly affectionate nickname “Platinum Blonde”. These people have gone way beyond the solving capabilities of any human solver. So whilst I may have claimed previously that the 2009 Zilina world record puzzle was as hard as it gets and that it’d be the puzzle Beelzebub himself would set you to save your soul – actually the behemoths these people whip up for each other you are doing extremely well to solve even if you use lots of trial and error. I recommend not even starting to attempt.

Now, on the other hand, some easy puzzles can be extremely elegant. Not necessarily in the techniques required to solve them in isolation, but how the techniques come together to form a complete and satisfying solve. What this could mean for example, is a puzzle that has a definite starting point, which leads directly to another deduction and so on – inducing a “continuous flow” to the solving experience. It may be a repetition of a particular solving technique, or it may be a particular visual pattern that emerges as you solve the puzzle. I guess much like any art form, there isn’t really a satisfying way to define what makes a beautiful puzzle – but even a complete novice can spot it and enjoy it when they see it.

Anyhow, that’s an awful lot to aspire to. I’m not quite sure how much of that I’ve managed to achieve with this Heyawake (if any at all), but I’m running out of time to fiddle with it today…

#020 Heyawake – rated easy

All puzzles © Tom Collyer 2009


June 05, 2009

Friday puzzles #3

Ok, so delayed a little later than Sunday. I’ve been busy.

On the other hand, here’s a sudoku with the givens in the shape of a Yin-Yang. Only I’ve just noticed that’s only true modulo a reflection – and we all know the sorts of trouble that quotienting out by an involution can get us into. So tomorrow I’ll put up a properly shaped puzzle. :)

Enjoy this incredibly easy fodder for now though!

#005 sudoku – rated easy

EDIT: Here is the new, improved, properly shaped and rather nicely themed version, if I do say so myself. However, the large number of givens really does mean that it is still very easy.

#006 sudoku – rated easy

All puzzles © Tom Collyer 2009


May 22, 2009

Tom Collyer writes some logic puzzles…

A.K.A. Friday Puzzles #1

Hello all. Recently I have taken up writing logic puzzles as an excellent means of wasting time – but also as a potential future earner. I am now at the stage where I am willing to publish them to the internet in a bid to firstly start a bit of a following, and a bit of feedback – and secondly to start buidling my own personal reputation. The idea is to start publishing a weekly puzzle that I have written myself. This is a learning process for me so the soving difficulty of my puzzles will probably vary wildly, but I’ll try and pigeon-hole them into three categories – easy, medium, and hard.

Anyhow, it ought to be fairly obvious that one of my favourite logic puzzles is sudoku, and so provides as good a place to start. Most sudoku you will solve tend to come from newspapers and books, and almost all of these will have been generated by a computer. The benefits of actually having a person make them I hope will become obvious as you solve these.

Please note that my puzzles are not all going to be sudoku. That’s not even close to what I aim to do. Where I publish a puzzle that is relatively obscure, I will post up the rules and perhaps a couple of examples of how they are applied. However, I’m sure everyone’s perfectly fine with sudoku, so without further ado:

#001 sudoku – rated easy

#002 sudoku – rated easy

All puzzles © Tom Collyer 2009


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Welcome to the blog of current UKPA sudoku champion, two-time Times national sudoku champion and general logic puzzle fan Tom Collyer.



Home of the original Friday Puzzles, each Friday I publish a 100% original and handmade logic puzzle, inspired by the world-famous Nikoli company.


How to play:
AkariFillominoHashiHeyawakeHitoriKakuroLITSMasyuNumberlinkNurikabeRipple EffectShikakuSlitherlinkSudokuSuraromuYajilin.

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Latest comments

  • I like the appearance of the solution. :P Nice one. by Prasanna Seshadri on this entry
  • I think I've seen something vaguely similar in some of Palmer's puzzles as well. To be honest I've a… by on this entry
  • That's two puzzles in a row where I find something I had used before. I know, not plagiarism; just g… by Bram on this entry
  • Kota, that's not really true. I had made my puzzle before going to the WPC already. Also I don't hav… by Bram on this entry
  • About 20 minutes, after restarting from a mistaken conclusion. by Bryce Herdt on this entry

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