2021 WPF Sudoku and Puzzle GPs

Information and discussion on Puzzle Competitions
detuned
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2021 WPF Sudoku and Puzzle GPs

Post by detuned » Fri 01 Jan, 2021 4:57 pm

Lets experiment with a combined thread this year :)

https://gp.worldpuzzle.org

The schedules have been published for 2021. In general there is one competition every fortnight, alternating Sudoku and Puzzles. [Note the slight break in that schedule for June however!] The first of the 2021 competitions happens in two weekend's time:

Sudoku GP 2021
1st round - 15.1. - 18.1.- Bulgaria
2nd round - 12.2. - 15.2. - Serbia
3rd round - 12.3. - 15.3. - Turkey
4th round - 9.4. - 12.4. - France & Hungary
5th round - 7.5. - 10.5. - The Netherlands
6th round - 4.6. - 7.6. - India
7th round - 2.7. - 5.7. - Poland
8th round - 30.7. - 2.8. - Germany

Puzzle GP 2021
1st round - 29.1. - 1.2. - Poland
2nd round - 26.2. - 1.3. - Hungary
3rd round - 26.3. - 29.3. - Germany & Bulgaria
4th round - 23.4. - 26.4. - Switzerland
5th round - 21.5. - 24.5. - Japan
6th round - 11.6. - 14.6. - USA
7th round - 16.7. - 19.7. - Slovakia
8th round - 13.8. - 16.8. - France

Feadoor
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by Feadoor » Thu 14 Jan, 2021 10:03 am

Sudoku Round 1 starts tomorrow, and the instruction booklet is available here: https://gp.worldpuzzle.org/content/instruction-booklet

pinkagape
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by pinkagape » Thu 14 Jan, 2021 7:52 pm

Any hints on Full Rank? Will there be four numbers starting in 1, four with 2 and so on?

Feadoor
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by Feadoor » Thu 14 Jan, 2021 9:15 pm

Yes - that's essentially all there is to it. Any clue in the range 1-4 must start with a 1, in the range 5-8 a 2 and so on. The rest is standard Sudoku and comparing the values within each range of four to get further restrictions. It can be a lot to keep track of so I strongly suggest crossing a clue out once you are certain from your notation that however you complete the grid from that point it will be positioned correctly relative to its immediate neighbours.

detuned
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by detuned » Fri 15 Jan, 2021 11:44 am

Yes sadly full rank is one of the tedious types where you need to know "the trick". They all solve in roughly the same way:

Ranks 1-4: digit closest to the edge is a 1
Ranks 5-8: digit closest to the edge is a 2
...
All the way down to Ranks 33-36, where the digit closest to the edge is a 9.

Then you start faffing around with the 2nd closest digit to the edge and so on.

Unfortunately there isn't really that much solving variety with this variation.

detuned
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by detuned » Fri 15 Jan, 2021 3:35 pm

Some other solving tips:

Diagonal consecutive: when using the negative constraint, bear in mind that if you have a 5 in a cell, then yes that rules out 4,6 in cells touching at a corner, but it can still be a 5. I often do that by mistake as the equivalent heuristic for consecutive sudoku would rules out the 5 (via the row/column constraint)

Diagonal 10s: similarly don’t forget that 5,5 is possible!

Feadoor
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by Feadoor » Tue 19 Jan, 2021 9:39 am

Preliminary results are out, the UK top 3 are:

32. Sam Cappleman-Lynes - 495
41. Jeremy Kong - 468
58. Tom Collyer - 412

The overall top 3 (Kota, Tantan and Tiit) are well clear of the rest of the field.

Puzzles-wise, I did not regret my decision to just keep guessing at the endpoints of the lines in the Extended Extra Regions until I found a configuration that solved. Perhaps I should have done that earlier though, before I spent nearly 10 minutes with only one digit in the grid.

detuned
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by detuned » Tue 19 Jan, 2021 12:46 pm

I didn’t have a go at extended extra regions during time, and was pleased that I didn’t. It reminded me of why I lost interest in the GP last year. There seems to be a growing trend of puzzles that I find hard because they are fiddly and there is no sense of flow to my solve - actually I'm finding they aren’t that much fun or satisfying to solve. Have other people noticed the same?

No individual deduction was difficult for the extended extra regions, but it was a narrow solve path with lots of the deductions placed randomly. To have a puzzle like that take up nearly 20% of the test’s points doesn’t seem like a great way to keep people interested! I doubt you were the only person Sam to have solved via case bashing.

I lost 40 points to a silly mistake and a further 20 to being inadvertently timed out (by about 6 seconds :/). Although I’m solving more for fun than for score, I’m happy to see I’m still vaguely competitive on the leaderboard.

Puzzle_Maestro
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by Puzzle_Maestro » Fri 22 Jan, 2021 11:30 am

The instructions booklet for round 1 of the puzzle GP is our at https://gp.worldpuzzle.org/sites/defaul ... nd1_IB.pdf

Looks to be a fairly unorthodox round, with a high concentration of maths/arithmetic based puzzles, around 75%. Of these the anti-knight products is clearly the worry; products is already hard enough as two (almost) uniquely solvable, disjoint puzzles, and if there’s a lot of ambiguity in resolving what goes in each row/column it could be very challenging. Suspect I’ll need to make a practice puzzle for this.

Prime paths doesn’t feel like it could plausibly have such high point values (all 21 2-digit primes is only 42 cells and should permit bifurcation on 2,4,5,6,8) but we’ll see...

detuned
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by detuned » Fri 22 Jan, 2021 3:48 pm

Isn't products more a case of needing to be methodical and meticulous? I can see the solving path being fairly narrow (but hopefully not quite as random as per the sudoku GP above!) - and maybe a bit more fiddly when combined with the anti-knight constraint. I expect it's going to be quite a large size, but the same old tricks (consider the larger primes first) are likely to apply. I suspect once you've got a few of those down then thats where the anti-knight will start to come in.

It's worth noting that for mere mortals taking the test, if you ignore that particular puzzle there is still over 600 points worth of puzzles to have a go at. I suppose it depends on how well you back yourself vs the testers. It may well fall quickly to a well-chosen bifurcation...

Puzzle_Maestro
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by Puzzle_Maestro » Fri 22 Jan, 2021 4:48 pm

The main issue I see is that with the anti-knight constraint there is no need for complete cluing, so the usual tricks may not be applicable. Then again it could be just be a large and fairly straightforward puzzle as you say, similar to last year’s Easy as Japanese Railway.

detuned
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by detuned » Fri 22 Jan, 2021 7:19 pm

Incomplete clueing would be nasty! I'd not thought of that (although admittedly I think there have been a couple of examples of normal products where they've left out a small number of clues). Although there's a small consolation: the other side to that is at least it makes it a bit quicker to know where you should be looking... (the hitori effect!)

jupilogy
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by jupilogy » Sat 23 Jan, 2021 12:35 am

detuned wrote:
Fri 22 Jan, 2021 3:48 pm
... for mere mortals taking the test...
Any tips for prioritising which puzzles to do for a first timer? I guess I should just go for the puzzles I find easiest first?

pinkagape
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by pinkagape » Sat 23 Jan, 2021 11:59 am

Yes, I would do my most comfortable first, then the highest pointers I thought might be doable so I might have some quick ones to squeeze in near the end of the time. Just my personal ordering.

detuned
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by detuned » Sat 23 Jan, 2021 1:50 pm

Yep it’s always a good idea to have done quicker points left to do at the end. Although there is sometimes a slight tendency for the puzzles with the least points available to be the ones that the testers found the easiest, rather than the easiest for me.

The reverse is sometimes true for very large point puzzles. Occasionally they turn out a little easier than expectations because the testers struggled rather than the puzzle being outride harder. That seems to happen less often though - anything with 100+ points is most likely going to very hard and time consuming. Anything over 50+ points is again likely to be difficult!

I’d also second going for the puzzles you enjoy the most first.

mwhite
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by mwhite » Sun 24 Jan, 2021 8:00 am

I'd also agree with starting with the puzzles you enjoy/are most familiar with first. Of course, it does depend on whether your aim is to maximise your score or just to enjoy the puzzles.

After doing a few competitions, I started to realise that there were some puzzle types I could consistently do relatively more quickly. For example, a 50 point Skyscraper and a 50 point Tapa theoretically should take the same time according to the test solvers. But I would probably do the Skyscraper in no more than half the time of the Tapa so I would certainly do the Skyscraper first, even though I enjoy both types.

One final thing on this type of entry submission - if you want to achieve the highest score possible for you, being very careful with the submission is worth the extra few seconds. For example, in the sudoku round last weekend I entered my solution to puzzle 7 in the answer box for both puzzle 7 and puzzle 8 so my perfectly correct answer to puzzle 8 sitting in front of me scores me no marks. I wasn't helped by 7A and 8A both starting "761..." but still a careless error costing 43 points.

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Re: 2021 WPF Sudoku and Puzzle GPs

Post by puzzlemad » Sun 24 Jan, 2021 10:03 am

All good advice there. I fully intended 'taking part' with the Sudoku round - had a quick look at the instructions and tips here first, then ploughed in. While waiting for the full print, I grabbed the first page, got stuck on a fairly simple one (realised later that I missed the placement of a 4), left that, tried the order one, only looking at the first three digits of each line - so went wrong, then tried another which I weent wrong on too - gave up at that point. Have since solved them all (albeit slowly) logically. The extended regions, apart from the first digit, I finished up putting all the candidates in, then eventually found the way into it.

So, it really helps to make sure that you understand all the rules to a puzzle. I've often made a puzzle far harder than it should be simply by forgetting one of the constraints. On puzzles that have more than one type combined your notation can also really help (or hinder).
On the angler's cave - the parity will help determine which fish each of the lines can be attached to.
Cave, don't forget that the cells that are not part of the cave must be connected to the outside edge, therefore, the no battenberg rule applies.

jupilogy
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by jupilogy » Mon 25 Jan, 2021 1:34 pm

Oh no, I hope you have better luck for the puzzle GP. Thanks for the tips! I was wondering, though, what is the no battenburg rule?

Feadoor
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by Feadoor » Mon 25 Jan, 2021 3:38 pm

jupilogy wrote:
Mon 25 Jan, 2021 1:34 pm
Oh no, I hope you have better luck for the puzzle GP. Thanks for the tips! I was wondering, though, what is the no battenburg rule?
In Cave, you have two things to keep in mind:
- The white cells must be connected
- The black cells must all connect to the edge of the board

Imagine you had a 2x2 square with a checkerboard pattern - blacks in opposite corners, and whites in opposite corners. The white squares would have to connect to each other, somehow, and no matter how you do it they will end up isolating one of the black squares and cutting it off from the edge of the board.

This means that the checkerboard (or, if you prefer, Battenberg) configuration can, in fact, never happen!

pinkagape
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by pinkagape » Tue 26 Jan, 2021 4:34 pm

Puzzle_Maestro wrote:
Fri 22 Jan, 2021 11:30 am

Prime paths doesn’t feel like it could plausibly have such high point values (all 21 2-digit primes is only 42 cells and should permit bifurcation on 2,4,5,6,8) but we’ll see...
Is this likely to be a mix of a path puzzle and some dominoes style logic? I struggled to start the example, but I didn’t try any dominoes style logic yet. Any ideas for identifying the start or end of the path? I found that messed with my logic not knowing.

Puzzle_Maestro
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by Puzzle_Maestro » Tue 26 Jan, 2021 4:57 pm

Yes, I found the dissection in the example was almost completely resolvable using essentially only domino-type logic (though of course invoking the parity properties of the path). Identifying the ends of the path only comes into play later on, both of which are forced by the fact that two adjacent dominoes in the path cannot share a number.

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Re: 2021 WPF Sudoku and Puzzle GPs

Post by puzzlemad » Tue 26 Jan, 2021 4:59 pm

jupilogy wrote:
Mon 25 Jan, 2021 1:34 pm
Oh no, I hope you have better luck for the puzzle GP. Thanks for the tips! I was wondering, though, what is the no battenburg rule?
I see that Feadoor has already explained. This is something that is important to remember in a number of different types of puzzles. YinYang is another one of those where you need to have two distinct areas.

pinkagape
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by pinkagape » Tue 26 Jan, 2021 5:21 pm

Puzzle_Maestro wrote:
Tue 26 Jan, 2021 4:57 pm
Yes, I found the dissection in the example was almost completely resolvable using essentially only domino-type logic (though of course invoking the parity properties of the path). Identifying the ends of the path only comes into play later on, both of which are forced by the fact that two adjacent dominoes in the path cannot share a number.
Sorry to sound silly, but by parity properties you mean like a checkerboard and it has to go white black white black?

Feadoor
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by Feadoor » Tue 26 Jan, 2021 6:58 pm

pinkagape wrote:
Tue 26 Jan, 2021 5:21 pm
Sorry to sound silly, but by parity properties you mean like a checkerboard and it has to go white black white black?
The observation I used for the example was that if you colour the grid as you say, all of the tens digits of the primes share a colour, and all of the units digits share a colour. And since 2, 4, 5, 6, 8 can never be a units digit, you already know which colour is which.

jupilogy
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Re: 2021 WPF Sudoku and Puzzle GPs

Post by jupilogy » Mon 01 Feb, 2021 9:46 pm

Do we have to wait for the results to come out, or can we discuss the questions when the test is over?

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