2011 UK Sudoku Championship (11-12 June 2011)

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PuzzleScot
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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by PuzzleScot » Sat 11 Jun, 2011 11:51 pm

Sadly I made a typo in the answer key for that one.
I go through the entered answer keys occasionally, and award points for puzzles where it is absolutely clear the person has solved the puzzle correctly, but has a single obvious typo . There have only been about 5 or 6 cases so far. All puzzle contest organisers do this.

Para, you will see on your personal results page that you have been awarded the points you deserve ;)

If anyone thinks I have missed any that fall into the single obvious typo category, let me know.

detuned
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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by detuned » Sun 12 Jun, 2011 6:20 pm

Some nice puzzles there - and would anyone here believe it if I said I made no silly mistakes? :roll:

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by Para » Sun 12 Jun, 2011 6:43 pm

PuzzleScot wrote:Para, you will see on your personal results page that you have been awarded the points you deserve ;)
Thanks.

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by PuzzleScot » Mon 13 Jun, 2011 2:20 am

The 2011 UK Sudoku Championship has finished!

Top 3 UK participants: (Full UK results)
1 Tom Collyer 148
2 David McNeill 142
3 Michael Collins 125

According to the UK WSC team 2011 qualification rules, Tom Collyer and David McNeill have qualified for the team! Congratulations.
Michael Collins is first reserve, should either of the above be unavailable to attend the WSC in November.

The top international competitor was Hideaki Jo, of Japan, with an outstanding score of 230! See the Full Results table.

Thank-you to Mike Colloby and Liane Robinson for organising the contest, and to all the contributors listed on the contest page for their puzzle contributions. Also, thanks to all 114 players from 30 countries who participated in our truly international event. We hope you enjoyed the puzzles, and that we will see you all again soon! Remember the UK Puzzle Championship will be held here in 2 weeks time (25-26 June 2011).

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by euklid » Mon 13 Jun, 2011 9:01 am

At the #17 Frameless Sudoku I am stuck at an early point. In box 7 (lower left) I have determined all but the 68 pair. But then I get a contradiction at column 3 and row 6. Thus I assume that my box 7 is not correct. I arrive at:
319
52x
47y
(x,y denoting the pair 6,8)
Where is my error? Help is appreciated!
[edit: I found my mistake, the box 7 is correct]
Last edited by euklid on Mon 13 Jun, 2011 9:39 am, edited 1 time in total.

detuned
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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by detuned » Mon 13 Jun, 2011 9:14 am

Nice! Like I said I was pleased to not make any entry errors, but I wasn't expecting a McNeill-topping performance there as I lost a few points not coming back to puzzles I'd started and "temporarily" left, as well as managing to pick up the hardest of the classics to do in the last 5 minutes and not quite managing it. If Puzzler are still supplying the Times championship I will have to get the practice in again!

Congratulations to David, Michael and everyone else. Big thanks to Mike and Liane for putting this together, Alan for overseeing everything into the wee hours of the morning and of course all the puzzle designers.

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by rob » Mon 13 Jun, 2011 12:34 pm

Thanks for the contest. Quite a few nice puzzles here. I particularly enjoyed the top-heavy sudoku. The frameless sudoku was also great.

I found the small consecutive sudoku quite hard -- thankfully I gave up quickly enough during the contest. I still haven't solved the Futoshiki and the no3-consecutive sudoku. I'd appreciate some hints or a walkthrough, for the latter in particular.

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by drsteve » Mon 13 Jun, 2011 3:26 pm

I'll echo the thanks to Mike, Liane and Alan and the congratualtions to Tom, David and Michael.

Found the Killers in particular rather fun, but thought there could maybe have been an easier Classic there - pointwise, I did the hard killer in about the same time that I failed to do the easiest Classic. Maybe that's just me, though.

Also spent an age not realising that a 0- clue in Calcudoku doesn't require the highest number in the first box. Duh!

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by david mcneill » Mon 13 Jun, 2011 6:10 pm

Congratulations to Tom and our brilliant international competitors. And thanks to Mike and Liane for putting this together. Lovely puzzles from Gareth, Vladimir, Rakesh, Deb and Rishi. Hope I haven't left anyone out.

I'm afraid I hated the Classic puzzles from Puzzler Media. These completely ruined my mood during the contest. Why I didn't throw them away I will never know. I would have had a much more enjoyable evening if I had skipped them and solved something nice. Just wasn't thinking straight. Not only were they tedious, they were also far too hard for the points available. Please no more of these. Or at least only one per contest.

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by rodders » Mon 13 Jun, 2011 6:44 pm

Ditto on the congratulations to Tom and David and many thanks to Mike, Liane and all authors and to Alan for the smooth running of the contest.

I have to agree on the Classics. After spending 1 minute on the first one, I decided to avoid them, although I definitely made a strategically poor move spending my last 25 minutes (narrowly) failing to complete the Top Heavy puzzle, when I could have picked up some definite points on the Kid Sudoku and possibly one of the medium puzzles as well. Being a bit less tired might have also helped! However, I would still have been well short of the necessary points to challenge.

All in all, a very enjoyable contest, thanks.

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by mikecolloby » Mon 13 Jun, 2011 8:01 pm

Well done Tom, great job!

It would be useful to get some more feedback so that we can make adjustments for next year. I've already got the point about tightening the definition of a Sudoku, and that the Classics should be a bit easier. Please don't blame Puzzler for this, because we selected the ones we wanted to use. What I would like is feedback on whether the objectives were appropriate, and whether they were met. The objectives were:
1. Puzzles should all be challenging, but not so hard that they rewarded guessing. Were there any that you guessed? Were any too easy?
2. There should be a number of puzzles at the beginning that new players can have a go at. This should have included the Classics, but it seems they were too hard. What about the other early puzzles, and this objective itself?
3. The end should make the top players sweat, but it should be possible to finish so that the winner has to solve everything and hence there is no benefit in cherry-picking. Clearly it was a bit too long by this definition. We estimated it would take the winner 133 minutes to finish, and this proved to be about right. On the other hand, LMI aim for quite a number of players to finish. What do you think?

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by drsteve » Mon 13 Jun, 2011 9:16 pm

mikecolloby wrote:Well done Tom, great job!

It would be useful to get some more feedback so that we can make adjustments for next year. I've already got the point about tightening the definition of a Sudoku, and that the Classics should be a bit easier. Please don't blame Puzzler for this, because we selected the ones we wanted to use. What I would like is feedback on whether the objectives were appropriate, and whether they were met. The objectives were:
1. Puzzles should all be challenging, but not so hard that they rewarded guessing. Were there any that you guessed? Were any too easy?
2. There should be a number of puzzles at the beginning that new players can have a go at. This should have included the Classics, but it seems they were too hard. What about the other early puzzles, and this objective itself?
3. The end should make the top players sweat, but it should be possible to finish so that the winner has to solve everything and hence there is no benefit in cherry-picking. Clearly it was a bit too long by this definition. We estimated it would take the winner 133 minutes to finish, and this proved to be about right. On the other hand, LMI aim for quite a number of players to finish. What do you think?
1. Well, I guessed a bit on the small consecutive, but that's the nature of the beast, I guess. Couldn't see a definite way in, so tried a few variations along the top. Don't think this one counts as challenging though.

2. I'd say the first few should be accessible and startable. I'd put a couple of relatively easy Classics (maybe even a 6 x 6 one) and then one or two simple variants - consecutive but with some givens, perhaps. I'll go along with the masses and say that the three non-sudokus really shouldn't have been there, especially not at the start.

3. Can't say much about this one, as I'm not a top player :) Not too keen on the Frame Sudoku though - it's one of those puzzles where if you know how to start it, you have a substantial headstart on someone who hasn't seen it before. Lovely puzzle, but I'd be curious what the top players think of it. Other than the two Killers being, to me, of similar difficulty, can't really say anymore about the later ones.

EDIT: Oh, and isn't Top-Heavy a sudoku version of another puzzle - Fuzuli? Maybe it should be renamed this. Nitpick, that one!

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by ronald » Mon 13 Jun, 2011 9:39 pm

In response to the request for feedback. Overall I really liked this contest, so good job! A nice collection of puzzles that were well tested and provided a great challenge.

These are the places I thought improvements would be valuable:

- I would add my voice to the people saying the classics were really too hard: not only rated with too few points compared to the other puzzles, but they were not accessible to beginner puzzlers.
A beginner-level easy 9x9 starter puzzle would really, really help!

- The killer grids were laid out significantly differently.
The easier killer had much thicker lines, meaning it effectively had half the writing area for notation.
I ended up throwing the easier killer away because of this.
The harder killer had a much better layout for puzzling.

In general, the grids were smaller than they could have been - bigger is better, and could have been achieved without costing too much white space.

- The answer key on the frameless sudoku was unclear.
Where the example had all clues given - the competition puzzle had all clues given apart from those where the clues had apparently been covered by the "R" and "C" answer key markers.

When I looked at this, I was at first concerned it could be a printing error or otherwise unintentional and therefore avoided the puzzle.
A clear distinction between the area where puzzle clues were given and answer key would have been beneficial.

In general, the competition would have benefitted significantly from a house style of puzzle grid.

- I felt that - perhaps - there were too many fancy puzzles for-the-sake-of-it, and way too much weighting on those compared to standard sudoku. I didn't complete it yet, and perhaps I've missed some exciting innovation that this provides... but (for example) "Diagonally Non-Consecutive" made me sigh.

And on the other hand... there was no "Sudoku X/Diagonal Sudoku" with the long diagonal 1-9 restriction... a favourite in UK newspaper(s).

How does this compare to the distribution of WSC puzzles?

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by uvo » Mon 13 Jun, 2011 10:08 pm

Hi Mike,
mikecolloby wrote:Well done Tom, great job!

It would be useful to get some more feedback so that we can make adjustments for next year. I've already got the point about tightening the definition of a Sudoku, and that the Classics should be a bit easier. Please don't blame Puzzler for this, because we selected the ones we wanted to use. What I would like is feedback on whether the objectives were appropriate, and whether they were met. The objectives were:
1. Puzzles should all be challenging, but not so hard that they rewarded guessing. Were there any that you guessed? Were any too easy?
2. There should be a number of puzzles at the beginning that new players can have a go at. This should have included the Classics, but it seems they were too hard. What about the other early puzzles, and this objective itself?
3. The end should make the top players sweat, but it should be possible to finish so that the winner has to solve everything and hence there is no benefit in cherry-picking. Clearly it was a bit too long by this definition. We estimated it would take the winner 133 minutes to finish, and this proved to be about right. On the other hand, LMI aim for quite a number of players to finish. What do you think?
I certainly agree with that objectives.
1. The puzzles I had to guess (or rather, do excessive trial and error) were the classics and the Futoshiki. I had some troubles with the nonconsecutives, but that may be my fault, not the puzzles'.
2. Especially the classics (or rather, some of the classics) should have been easier. It is strange that the only easy puzzles in a Sudoku competition were not Sudoku at all :-)
And compared to other puzzles, the classics all gave far too few points. Judging by how much time I spent on all the puzzles, the classics should have been worth about 16-20 points (maybe somewhat less, because I am no classic specialist).
3. If the competition acts as qualification for another championship, I prefer contests that do not rely on time bonus: if there are, say, 3 WSC spots, then it feels awkward if four players finish all puzzles and only three qualify. Of course, the situation is similar if these four players finish all but one puzzle, but it still feels different to me. So, in that case, it would be fine if 1-3 players are able to finish all puzzles, but not more. (I know it is difficult to judge that in advance, but that would be my objective.)
One more point: if it is a UK championship, I wouldn't worry about top solvers from other countries. Decide what results you would prefer from the top UK competitors, and set your timing accordingly.

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by detuned » Mon 13 Jun, 2011 11:23 pm

I thought the classics were on the edge of being fair - but perhaps a more varied spread of difficulties would have been a better move. Perhaps this is because I know that from past TImes championship experience I can solve 4 of these challenging Puzzler offerings quicker than any UK competitors can guess at them. I have known worse at a championship (when sudokusolver.com were the suppliers) - multiple x-wings and and swordfish thrown in - but again I managed to win that on account of being able to spot the relavent tricks more efficiently than the competition could guess.

On a more positive note for Puzzler, I thought their killer generator stands up really well amongst some quality hand made puzzles. I wonder how many people realised the 2nd killer was in fact from the generator? Said generator even managed to elicit some begrudging praise from Dr Snyder in Beijing after I showed him the killer I was solving in the paper on my flight out.

The futoshiki I found solved relatively quickly, although there was an x-wing to spot.

With consecutive puzzles, often the work-in is to have a big chain of consecutive numbers where the direction isn't quite determined but a contradiction soon becomes apparent. As previously mentoned, this is simply the nature of the beast.

I agree with Ronald's comment about having a unique house style. Mike briefly mentioned some of the logistics with regards to organising puzzles from numerous different sources, and I can only imagine there was not enough time to restyle everything. I'm sure either Gareth or I can offer some advice about this for future contests.

Re distribution of puzzles, I think I'd have definitely have expected to see an irregular and a diagonal puzzle as part of the standard variant package - but actually aside from having calcudoku/futoshiki/skyscrapers instead of their sudoku variant cousins I think this definitely nailed the objective of having a WSC style mix together with appropriate difficulty levels.
Last edited by detuned on Tue 14 Jun, 2011 8:59 am, edited 1 time in total.

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by debmohanty » Tue 14 Jun, 2011 1:25 am

Mike,

3] Since LMI monthly tests have a different purpose, it is best not to be compared.
Like uvo mentioned, in case of national championships, the timing should be set according to best UK solvers. It shouldn't matter if top players from other countries finish all puzzles in x% of the allocated time OR if y top players from other countries finish all puzzles in the allocated time.

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by GarethMoore » Tue 14 Jun, 2011 1:39 am

I really enjoyed the contest even though as a competitor there were several puzzles I couldn't do since I'd supplied them - with the extra 16 points I'd have safely got from the first 3 puzzles I'd have done (for me) pretty well.

I think for a tournament it is very important that we immediately delete posts here which reveal information about the test - both the two at the bottom of the first page of this forum thread say or at least strongly imply that the classics were too hard and the frameless sudoku was hard. Noticing people skipping the classics in the results table I wonder if this influenced people - at the very least it will encourage you to skip quickly once you get stuck, not look for something 'obvious' you've missed. It certainly influenced me, although I decided to try them anyway. Certainly I thought that they were all too hard relative to the other puzzles for the number of points assigned, and it would have been nice to have had an easy one.

I thought the 6x6 consecutive I'd sent was pretty hard for its size but once you write in the candidates in the top-left box and see how it connects with the top-right box it falls out pretty quickly - compared to the 8 points for the sudoku I think those are 7 relatively easy points. I think the expectation is that 6x6 sudoku will be easy, so it's a bit upsetting when they aren't. :) The Futoshiki needs an x-wing, as Tom pointed out - it's tricky but definitely a much easier puzzle for 14 points than the 8-point sudokus.

In terms of the Frameless Sudoku, Deb had kindly sent 4 for the previous issue of Sudoku Xtra magazine, so I was lucky enough to have already tried them and discovered they were excellent but tough! :) So I knew to skip that. ;)

I really enjoyed the kid sudoku in the test and in the IB - I'd not tried one before and thought it was much more fun than it looked. For me I found that having both No Donkey Step and Diagonally non-consecutive in the test was very confusing - I messed up both because I kept confusing the two rules. I got confused over these when practicing in the IB too, mind. Having both in the same test was either an excellent assessment factor or a bit too much depending on your point of view. :)

I thought the Top Heavy puzzle was great - good fun and no difficult logic. Similarly I knew from the IB that the Palindrome Sudoku might be easy (even though jigsaw sudoku are my nemesis - I can't usually do them at all), and it was. Probably both much easier for their 20 points than, say, the 14-point consecutive sudoku, which needs much tougher logic.

Finally in terms of layout, I think getting the puzzle resolution (and size, as Ronald said) right is more important than a consistent style. I know the files I sent were vector format (no pixels) but when they were pasted in they seem to have become quite pixellated, particularly in the IB. If you're pasting from Acrobat Reader into Word then just zoom in before you copy and paste. There are also colour screen-grab artifacts in many of the puzzles if you zoom in (from LED sub-pixel aliasing) - the saturation should be set to 0 in something like Irfanview before the art is used. I wrote an article in the members section on this before.
Last edited by GarethMoore on Tue 14 Jun, 2011 2:06 am, edited 8 times in total.

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by motris » Tue 14 Jun, 2011 1:40 am

A few (unsolicited) comments from a non-competitor - I will not compete in any sudoku championship that isn't 100% a sudoku championship - but I did go through all the puzzles and think you put together a really great 16 sudoku set.

1. Timing: If the target timing was about 2 points per minute, then the expected timing of 133 minutes pretty well matches my experience. I was closer to 123 minutes over the sudoku and the extra fodder, but without answer entry or competition pressure, so I think your goal was spot on. A few variants were overvalued (Palindrome certainly) and others undervalued (Frameless, but maybe I just am hesitant to have to start a puzzle with a guess), but not a lot of outliers.

Still, I don't think a national championship should be set so even a world champion is unlikely to finish, as this means the effective UK qualification line may be at around 50-60% of points. At this low level, "puzzle selection" becomes a much more important factor relative to sudoku solving ability, as can specialties like arithmetic skill that are not themselves as strongly rated at a WSC when there were 76 points by my estimation that strongly valued arithmetic, about 30%. A better goal is probably 80-90% completion. See also uvo's post, as his comments are spot on.

2. Classics: My four classics times were 3.5 to 5 minutes, so exactly 2 to 2.3 points per minute. I'm not the fastest classics solver, but I am a very balanced solver. I am shocked by the apparent apoplexy of some of the top solvers in this forum about these classics. Then again, I had the same shocked response when this UK forum seemed to uniformly state that the classic sudoku on the 2010 USPC was too hard. I'm coming to realize the UK may not actually know how to evaluate "hard" puzzles. These were 4-star (or 400m) sudoku, but 100% fair, with logical solutions and basic steps. The hardest thing I might have to describe is "spot the naked pair in column 8" and that seems right to me. For comparison to what is actually hard (unfair), take a look at Rishi Puri's Sudoku Mania on this same site which was a good test save for its single Classic Sudoku which needed X-Cycles, AICs, and then eventually some XY-chains to solve. I still can't logically solve that puzzle and I still am very frustrated it occurred on the test. There was nothing obnoxious or overly difficult with these classics.

So while I'd say that the puzzles were the fair kind of hard, they were also too much of the same level of challenge, and you would be better served next time with perhaps 5 classic with 1 very easy, 2 intermediate, and 2 of this level. Drop the 3 fodder puzzles and the resulting test would be well balanced. Perhaps you want more classics anyway (or variants like Diagonal that I'd consider as the same), as at the moment the top scorer of this test still hasn't solved any. 230 is impressive by H.Jo, but that score avoided all the classics!

3. WSC balance - compared to all my WSC experience, this test had more 10+ minute puzzles than any round I've seen in 5 years of competing and organizing. Having a few of these is ok, but I felt a better balance might have been obtained with a few more 3-5 minute variant puzzles (10 pointers) compared to 20+ pointers. Keeping about 18 sudoku puzzles but having several of them slightly easier should get the final scores for a 2 hour test in the right level, and really select exactly who will perform best at a WSC. You aren't far off, but you aren't perfect yet.

Outside of these comments, this is a promising first qualifier for the UKPA and I look forward to seeing more in the future. Thanks to all the puzzle contributors.

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by motris » Tue 14 Jun, 2011 1:56 am

detuned wrote: On a more positive note for Puzzler, I thought their killer generator stands up really well amongst some quality hand made puzzles. I wonder how many people realised the 2nd killer was in fact from the generator? Said generator even managed to elicit some begrudging praise from Dr Snyder in Beijing after I showed him the killer I was solving in the paper on my flight out.
Corrected your typo. I don't go by either Tom or Mr. anymore. I'd repeat the same begrudging praise here on the 30-pointer. The stack on the far left had moments of seeming brilliance in how fixed sets work and feed digits like 7's. But the two others lacked the same cohesion to throw the CPU design back into question. Rishi's was definitely more interesting visually and logically, but I'd have to say Puzzler has a really good generator for this type. I was also quite amused that Puzzler's classics featured 3 of 4 puzzles with non-traditional symmetry.
Last edited by motris on Tue 14 Jun, 2011 2:11 am, edited 1 time in total.

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by GarethMoore » Tue 14 Jun, 2011 2:04 am

motris wrote:I was also quite amused that Puzzler's classics featured 3 of 4 puzzles with non-traditional symmetry.
I know you don't get them in the US, but in their hundred or so different magazines Puzzler use, completely randomly, horizontal, vertical and diagonal mirror symmetry (along with more traditional symmetries).

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by drsteve » Tue 14 Jun, 2011 6:06 am

motris wrote:
2. Classics: My four classics times were 3.5 to 5 minutes, so exactly 2 to 2.3 points per minute. I'm not the fastest classics solver, but I am a very balanced solver. I am shocked by the apparent apoplexy of some of the top solvers in this forum about these classics. Then again, I had the same shocked response when this UK forum seemed to uniformly state that the classic sudoku on the 2010 USPC was too hard. I'm coming to realize the UK may not actually know how to evaluate "hard" puzzles.

There was nothing obnoxious or overly difficult with these classics.
There was nothing obnoxious or overly difficult with these classics ... to you, Tom.

As a decent puzzler and a better than average sudokuist, I found these classics difficult and time-consuming. As everybody else who mentions them on this message board seems to be of the same opinion, then I would suggest that these are, in fact, hard puzzles and you are simply good at doing hard puzzles.

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by PuzzleScot » Tue 14 Jun, 2011 9:17 am

Still, I don't think a national championship should be set so even a world champion is unlikely to finish, as this means the effective UK qualification line may be at around 50-60% of points. A better goal is probably 80-90% completion. See also uvo's post, as his comments are spot on.
I'm keeping these comments in mind for the upcoming UKPC. Thank-you.

I have tried to gauge what top UK solver times would be as realistically as possible. I'm currently standing at <=2h50m expected total solve time (<=2h10 for top international) with a 2h30 window. The nature of logic puzzles is that everyone's solving experience is different, so I believe it is possible for a Brit or 2 to finish, just. I'm reluctant to make it much less.
Proof of the pudding is in the eating! We shall just have to see how it goes, and learn for next year.

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by PuzzleScot » Tue 14 Jun, 2011 9:57 am

motris wrote:I will not compete in any sudoku championship that isn't 100% a sudoku championship
I presume you meant "...sudoku...that isn't 100% sudoku..."?

Will you be good for the UKPC the weekend after next? I can guarantee that it is 100% puzzles, with not a sudoku to be seen! ;)
Although some gentle bifurcation may be required...

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by detuned » Tue 14 Jun, 2011 10:25 am

motris wrote: Corrected your typo. I don't go by either Tom or Mr. anymore.
Fixed it on my end too - a careless slip!

So I'd like to think I can solve a hard-but-fair sudoku and recognise one when I see it. I think the issue here comes down to speed solving. I still recall the Times championship in 2006, the last time David participated. I recall being paired off against him in a semi-final - puzzles again supplied by Puzzler - and ended up being slower overall than him, despite him bifurcating at one point and a little later rubbing things out quite frantically. Now I'm a far stronger solver now than I was then (that was my first puzzling competition of any sort) and I'd like to think that wouldn't happen to me again - but I can certainly understand David's frustration with the puzzles if he feels he has to bifurcate to achieve his best solving times.

Finally - re hard-but-fair classics - I appear to have been singled out for a few comments (again) on the pick of the sudoku on nikoli.com. I had a little smile when I saw the "hardest ever" comment as it struck me as being a little hyperbolic by my standards, buy I certainly remember being gazumped by it at the time, and even resolving it after it appeared in the pick it was still an 8 or 9 minute solve. This despite having no one step that was even remotely unfair. Does anyone have any other thoughts on that?

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Re: 2011 UK Sudoku Championship (11-12 June 2011)

Post by motris » Tue 14 Jun, 2011 3:21 pm

Sure. I guess I'd simplify my comments by saying there are two axes of difficulty with a sudoku. They can have easy or difficult (or non-existent) logical steps. They can have a broad or narrow solving path (meaning fewer places to make the next deduction). These have a low score on the type of step axis and a very high score on the solving path axis. For those who don't track where they have and haven't looked as well, these puzzles can have the feeling of "I'm not making any progress" or "It's coming in fits and starts". These are at the difficulty many WSC classics get on the breadth of solution axis. There are certainly also classics that go to crazy spaces on the other axis, like "Goes to 11" and "Guinness", but the point is these are not specifically inappropriate puzzles for a WSC qualifier. It just would be friendlier to have a few easier puzzles too.

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