Friday, 12 June 2009

Friday puzzles #4

Following its incredible introduction to the world in the finals of the first sudoku world championships in 2006, the toroidal variant gets the pulse of any enthuasiast racing. My effort is in much the same spirit as that original.

The rules are: Fill in each column, row and each region with the numbers 1-9. Some of the regions run off (for example) the top edge of the grid. They continue up from the bottom edge of the grid. Similarly with the left/right edges. The idea is that if you take a nice square, glue left side to right side, and then the top edge – now a circle – to the bottom edge you get a torus – and hence the adjective toroidal. Although if you too are a dabbler in the dark arts of pedantry, you will have noticed that actually a classic sudoku is also “toroidal”. But arguably not as hard. :)

All that is left to be said is this puzzle deserves a slot by itself. Back to two (or more) next week!
    #007 toroidal sudoku – rated hard
All puzzles © Tom Collyer 2009

P.S. The next 2-3 Friday’s might suffer some delays too. I’d say there is approximately a 1/7 chance of the puzzles being published on a Friday, but I’ll nevertheless try to keep to the deadline!

Saturday, 6 June 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

Friday, 29 May 2009

Friday Puzzles #2

Ok so this is getting a bit late now; on the other hand perhaps it’s not if you live in Hawaii. That’s the way it goes.

This week’s offerings are two Nikoli staples.

Masyu is a loop puzzle, where you try and join a loop in a grid containing white and black circles. The loop must pass through each of the circles; through a white circle the loop must go straight through, but then makes a 90 degree turn in one of the next squares. At a black circle, the loop makes a 90 degree turns, and then extends on in a straight line for at least two squares. See more here.

Nurikabe is an islands puzzle. You are given a grid of squares which must be coloured white or black. Each of the given numbers lies in an island comprised of the relevant number of white squares. Surrounding each island is a sea of black squares, subject to certain restrictions. Firstly the black squares are all connected, and secondly, given any 2×2 block of squares, at least one must be white. See more here.
    #003 Masyu – rated easy
    #004 Nurikabe – rated medium
All puzzles © Tom Collyer 2009

Friday, 22 May 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

Monday, 18 May 2009

WSC Zilina report part 7

This time I had a co-solver, Giulia Franceschini of Italy. Like I say I normally get annoyed with people pointing stuff out to me whilst solving, but a pretty face paired with actually being a pretty handy solver helps a lot. I’m really quite smug to say that our joint efforts had whopped Thomas and Wei-Hwa’s individual efforts (although both had used actual sudoku grids together with the unhelpful third 1-9 constraint). On the other hand, the slow process of drawing out the grids and regions and numbers wasn’t quick enough to trump the new 2009 World Sudoku Champion, Jan Mrozowski of Poland. I will point out that we were equally as handicapped as we were solving literally stood up with the paper held out in front of me.

And that was that, or so we thought. Apparently the Turks had a complaint about some aspect of the final – I didn’t quite understand what the grounds were, but there we go. What now added to the confusion was that the 4d sudoku guys were (apparently – I merely speculate here) not quite impressed by the slightly modified rules by which it was “solved” in the team rounds, and had appeared to spontaneously have organised an extra round whereby the 8 finalists would try and solve the puzzle proper in 15 minutes. This is as ridiculous as it sounds, but at this stage, we weren’t quite sure whether this constituted some sort of extra final play-off, due to the Turks’ complaint not being resolved. More than that, this time they’d actually be up on the stage in view of everyone. Again, no-one had any idea whatsoever what was actually happening. Another notch up on the Snyder scale of ridiculousness no doubt, but by this point Thomas was hammering out his viewpoints onto his livejournal page.

This did, however, give me the chance to get pun of the championship. This is a self-awarded title admittedly, but aside from an award for the most stupid semi-finals preparation it’s the only tangible prize I could take back with me from Zilina. As the bearded brothers in their garish black and orange self-branded polo shirts tried to explain the rules of their puzzle again, they mentioned the key to the puzzle was that there is exactly one blank outer face on the cube. My interpretation – given the confusion – was that there were actually eight blank faces up there on the stage. Well, at least Nick Baxter liked it a lot.

Rather appropriately however, this stupid distraction – it turned out the Turks’ complaint was not upheld and indeed Jan was still World Champion – was overshadowed when at the American’s table, Wei-Hwa had announced he’d finished the puzzle. Given his break to simulsolve the final puzzles, he’d managed it in about three quarters of an hour, which is probably as fast as anyone is EVER likely to solve the puzzle from scratch. Suddenly attention diverted from the stage to Wei-Hwa, and even the bearded brothers abandoned the floundering finalists to congratulate them. The Japanese finalist, Ko Okamato summed up the mood best as he sat up on stage, slumped in his chair, ignoring the puzzle and instead sat there sulking. Fair enough to the guy.

Still, I have no hesitancy in saying Wei-Hwa’s is one of the finest minds on this planet – if anyone was going to whop the puzzle it was him. He remarked to me that there was definitely a clear logical process that had guided his solving rather than mere trial and error, and I am quite happy to take the guy at his word. Although the teams were allowed to keep one puzzle each, I have no desire to addict myself to something else. I suggested to Ariane that she might like to give it away with one of her magazines.

And that was that for competitive sudoku. In theory this was now time for a little bit of socialising, but instead, a myriad of entertainers – including a mime artist, a troupe of kids from Slovakia’s got talent, some dancers and what appeared to be didgereedoo players. Some people were still puzzling however, and I drew out both puzzles for David, and watched him solve. Again the huge sizes makes a difference but he completely caned both puzzles up. If he’d have been in the final I’m fairly sure he’d have been the champion – and a well deserved one too! There’s always next year.

Did I mention the dancers by the way? Their first set resembled some Bollywood dancing, possibly because last year’s WSC . I presumed the next set was meant to represent next year’s lot in America – but frankly it was the sort of raunchy debauchery you’d associate with the Moulin Rouge. David, as a very committed married man, did his best to try and avert his gaze. Thomas too seemed more concerned with his livejournal posting on his laptop – but everyone else’s attention was drawn to the stage. Man, it was hot!

The entertainment dragged on, and at some point there was a presentation for the winners – the home crowd was happy as the Slovakians had won the team competition marginally ahead of the Czechs – but it wasn’t terribly exciting as I didn’t really know any of the winners. We grabbed some buffet dinner, and again I applied my Rootes restaurant strategy of taking one plate, and piling it high with as much quantity and variety of food as is physically possible. After dinner, I had an inspiring conversation together with David, Mike and the Americans Nick and Will Shortz. Unofficially speaking, they were looking forward to bettering the efforts of the Slovakians for the championship in Philadelphia next year. Some rather tongue in cheek variants were put forward – David mentioned trying to get the idea of Kerplunk! into sudoku – but I liked the idea of some electronic tetris variant, together with cheesy 80’s music and charming pixelated graphics!

The celebrations had already begun, and we met one of the Germans (Hubert Wagner I believe) who had been sent to the hotel bar to bring more wine for the Germans. They had seemed to have been locked in, so we gallantly offered to help him with his two bottles. Eventually the rest of the Germans came out to get the rest of their drink. More fun was to come as the Slovakians came up, together with some ice cold bottles of slivovica and marhuľovica – being plum and apricot brandies respectively.

The thing here is that with spirits that cold, a small layer of pure alcohol forms on the top of the shot – which I might add are rather larger than shots as we in the UK know them – the layer then pretty much forcing you to down in one. The apricot at 40% was slightly less severe than the plum at 50% ABV – and watching the Irish boys at work was quite a spectacle. Another fantastic quote from them was:
We’re not actually better drinkers than the rest of the world. We’ve simply got a reputation to uphold!
After a couple of downed “shots” they were really struggling. It should come as no surprise however, that the drinks rapidly disappeared – and being a Sunday evening the hotel bars has closed relatively early. Thus we were in the situation at midnight whereby a lot of us wanted to drink more, and some of us who didn’t want to go to bed because they had to start their journeys back at 3am. The only solution was to head out into town.

It had all looked very disappointing as we headed back to the town square, as being midnight on a Sunday everything was shut. And then the Gods smiled upon us – one lady who had just finished closing up her bistro place come and said she could reopen for a large group of well-paying tourists. This is possibly the best thing ever. We drank lots of beer, and were even able to order some pizza. Gradually people did drop off however, and by half 5 in the morning the owners balanced the money/sleep balance into the favour of sleep and kicked us all out. I was left walking back to the hotel with a Times reporter as the sun rose, and as the rest of Zilina appeared to be getting up for the start of a working week. Strange indeed.

And that, I believe is a good place to finish. Well almost. I had to be on a train to Bratislava at half 8 – and only just managed (by 45 seconds!!) to make it. I had slept unti five past eight and had to sprint, bags and all, to the station. My Slovak as I hurried tried to buy tickets was exemplary. The rest of the journey involved lots of sleep, and being poisoned at some dodgy tapas joint in London. But that’s another story.

Thanks for reading!

Contact Form

Name

Email *

Message *