WSC Practice #9: Round 12 - What Is It?

This is the 9th practice puzzle for the 2017 WSC.

These are the last 2 practice puzzles for the WSC. I'll be focussing on the WPC a bit for the next week. That's the championship where I'm actually competitive. I don't know whether I'll be posting puzzles yet for the WPC, but they might show up.
Nine posts also seems the appropriate number for a Sudoku competition. This time they are two practice puzzles for the instructionless round.
If someone has any specific request for a puzzle type, I might be persuaded to make another. Let me know.

I figured this is a round that might need some practice too. I don't think for either puzzle the rules are too hard to figure out. It's possible that both ideas have been done before. I can't remember seeing them before, but my memory isn't perfect. They're not exactly innovative ideas.
I think the first puzzle is probably more like a puzzle in the actual test. It's a just simple addition to a Sudoku grid. I had fun writing them, but with a bit more time I could have made them a bit nicer.
The second puzzle I'm not sure whether it qualifies as a Sudoku puzzle. It has all the rules of a normal Sudoku puzzle but it doesn't uses numbers like most Sudoku puzzles. I think the rules are pretty simple. I had a lot of fun writing them, so they should be fun to solve, I think.
Try the examples too. They're both fun puzzles too.

Rules for Sudoku

In this Sudoku the additional rules are not given. An example and solution are given of the Sudoku variant. Figure out the additional rule from the example and solve the puzzle.

Rules Puzzle #1 (highlight if needed): Each marked 2-cell area contains a 2-digit number, read left to right or top to bottom. The first marked 2-cell area seen by an arrow must contain a larger 2-digit number than the arrow.
Rules Puzzle #2 (highlight if needed): Place 8 arrows (fghimlkj) once in every row, column and marked 3x3 area. Numbers in the grid indicate how many arrows are pointing at that cell.

Puzzle #1

Puzzle #2

 

WSC Practice #8: Round 13 - Puzzle 7: Joker Product Sudoku

This is the 8th practice puzzle for the 2017 WSC.

The Joker round is going to be a tricky one. I made an error in the construction of the previous Joker puzzle. Hopefully There are none in these. It's easier to make an error in these puzzles if you just fall back into your standard deductions.
This type actually appears twice in the championship as it also appears in the final team round.
The first puzzle should be a nice solve. I put in a few things that can be done with the Joker in this genre. I'm pretty sure they were easily figured out by yourself, but I think they're nice to see in a puzzle. There's still a few key deductions to find, but it should work well.
The second puzzle is much harder. It relies on a lot of clue interactions, without giving much direct information. It takes a long chain of interactions to place a few digits and consequently figure out the Joker. Even then it's not exactly easy.
I had to check a possible error. I realised I might have forgotten something, but it didn't really influence the puzzle as the deductions still held true. The dumb construction errors really don't allay my fears of making errors in this round by accidentally forgetting a Joker interaction.

Rules for Sudoku

In this Sudoku, numbers on the borders of two cells indicate the product of the digits in those 2 cells. Additionally, there is a Joker digit in the grid. This digit can take on any integer value from 1 to 9 necessary to comply with the rules. It can even take multiple different values within a single cell to satisfy different clues.

Puzzle #1

Puzzle #2



WSC Practice #7: Round 7 - Puzzle 3: Japanese Sums Sudoku

This is the 7th practice puzzle for the 2017 WSC.

I know this round might be a bit contentious to some people. They're afraid it's going to be too puzzly and not enough Sudoku. But just because a Sudoku is named after a puzzle genre, doesn't mean it's completely like that genre. I have a few ways I can imagine these puzzles to be far more like a Sudoku than a puzzle.
I tried to design this Sudoku to not heavily rely on being familiar with Japanese Sums as a puzzle. The logic needed isn't much different than a Killer Sudoku. This is one of the ways I imagined the Sudoku element to shine much more through than the Japanese Sums element of the puzzle. The puzzle shouldn't be too hard if you work the clues in the right order. I hope this helps prepare a bit for the championship.

Rules for Sudoku

In this Sudoku, shade some cells in the grid so that the numbers outside the grid represent the sums of the digits in the white cells in that row or column. The sums are given in the correct order. If there are multiple sums in a row or column, they need to be separated by at least one shaded cell. Some shaded cells may be given.

WSC Practice #6: Round 9 - Puzzle 6: Crossed Sudoku

This is the 6th practice puzzle for the 2017 WSC.

This is not a very new variant. There's been similar variants, one of them being Shaken Clones Sudoku, where digits have to be the same within certain shapes. The only thing different seems to be that the shape is set for this variant. I haven't solved many of these though, so I figured writing one would be good practice for me.
This puzzle is pretty standard. There's not really anything difficult in this puzzle. It just explores the standard things in this genre. If you want a more challenging version of this puzzle, you can remove the 2 in R5C5. The puzzle is still unique that way, but the solving process gets a bit more complicated. You can still get through it logically, but it really isn't that nice. I had made a bad deduction in construction, but it somehow hadn't affected uniqueness. I only found out in the resolve. I decided to add the 2 to just have a smooth solve again.

Rules for Sudoku

In this Sudoku, all crosses contain the exact same 5 digits in any given order. Digits may repeat along a cross.

WSC Practice #5: Round 6 - Puzzle 9: Big Small Count Sudoku

This is the Fifth practice puzzle for the 2017 WSC.

I wasn't really sure how this variant was going to work. The example has a lot of givens, so I wasn't sure how it would work from that. I set up an opening section and figured I'd go from there. The opening section actually gave more information than I expected and I managed to reduce the second half of the puzzle a bit. It wouldn't get unique though, so I added an extra circle just to fix a small uniqueness issue. It doesn't make for the prettiest Sudoku, but it's a nice result anyway.
I generally like these kind of circle count puzzles, because it gives a fun interaction. Every time a circle gets figure out, a bit of new information gets revealed. It's like you're adding extra clues to the grid during the solving process.

Rules for Sudoku

In this Sudoku there are a number of circles. A digit in a circle indicate either "the number of neighbouring digits bigger than that digit" or "the number of neighbouring digits smaller than that digit" or both. Not all possible circles are marked.

WSC Practice #4: Round 13 - Puzzle 9: Joker Battenburg Sudoku

The fourth practice puzzle for the 2017 WSC.

I feel this round can use all the practice necessary. The Joker rule is something new, as far as I'm aware, and seems to be a bit tricky. Basically the Joker only follows the standard Sudoku rules, but ignores any variant in the puzzle. This is because the Joker digit can assume whatever digit it needs to be for the puzzle to work, even if it means being different digits in the same cell.
The Battenburg Sudoku was one of my own inventions. The reason I picked this type first is because it has both a positive and a negative rule in effect as all possible markings are given. The "All possible markings" rule is a bit odd with the Joker. The way I understand it, in the given solution there are no places where any extra markings HAVE TO be placed. Even if there are markings that could be placed if the Joker assumes the correct parity, they don't have to be placed as the Joker can assume an incorrect parity. I do hope my interpretation is correct, but it seems to conform with the given example in the Instruction Booklet. If it isn't, my apologies for providing an incorrect puzzle. It has happened before. It should still be fun to solve.
I think the puzzle worked out pretty well. The opening should properly show the way this variant interacts with the Joker. Once you've determined the value of the Joker, the solve really takes off. It's probably a harder puzzle because you have to keep reminding yourself of the Joker rule and thread carefully through the puzzle.

[Edit: Puzzle image fixed.]

Rules for Sudoku

In this Sudoku, everywhere a 2x2 square forms a Checkerboard pattern of Odd and Even digits a Battenburg marking is given. All possible Battenburg markings have been given.
Additionally, one digit in the puzzle is a Joker. This Joker digit can be both Odd or Even. The same Joker cell may assume different parities for different 2x2 areas.

 

WSC Practice #3: Round 6 - Puzzle 1: Incremental Arrow Sudoku

This is the third practice puzzle for the 2017 WSC.

Obviously some of the puzzles are going to come from the 6th round as it has new types. I figured I might as well start at the beginning of the round. This also seemed like a type that would suit my writing style.
The overall design idea was to make a long arrow and match the givens in the same place. I think it worked out well. The other 2 matching arrows just add a little bit extra to the aesthetics. This is probably the easiest puzzle out of the three practice puzzles so far. It's really a matter of making one single opening deduction and the rest of the puzzle flows pretty easily.

Rules for Sudoku

In this Sudoku, there are a number of arrows. Starting from the third digit on the arrow, each digit is the unit's digit of the sum of the previous two digits on the arrow.

WSC Practice #2: Round 1 - Puzzle 5: 12 Sum/Product Sudoku

The second practice puzzle for the 2017 WSC.

This second puzzle is a type I don't necessarily remember solving before, but it's not exactly a new type. There's been numerous similar variants with products and sums, but this one only uses the number 12. It is the 12th WSC, so it isn't that surprising a twist.
It's impossible to write a puzzle without any given digits, as there is no way to differentiate between a number of digits. So I decided to find a nice layout of givens and work with that. The centred 1-9 is always a nice layout to choose and it actually led to some nice interactions with the 12-dots. So I designed the rest of the dots around that to make the puzzle unique. I think it worked out well. I can't really judge the difficulty, although it might be trickier than it felt designing as one deduction came about by accident as I missed it was forced pretty much from the start and went with it. Hope it's useful and fun to solve.

Rules for Sudoku

In this Sudoku there are a number of grey dots between cells. If there's a grey dot between two cells, the sum or product of the two digits in these cells must be 12. Not all possible dots have been marked.

WSC Practice #1: Round 2 - Puzzle 22: Outside 234 Sudoku

This is the first proper practice puzzle for the 2017 WSC.

I've written this type a couple of times, usually under the name Inside Sudoku. One of them was used at the 2016 Thai Open and another one can be found on my blog. The logic is pretty similar to Outside Sudoku, but the small twist makes it different enough to qualify as a different variant. Because it's a newer variant, I enjoy writing these a bit more.
This puzzle has a type of opening that works nicely in this variant. I think you need to fully understand the implications of the opening to get your way through the puzzle. It's not the easiest opening, but should be useful to understand the full implications of this variant. The solve around it shouldn't be overly hard. I sacrificed symmetry a bit to keep a nicer solve. I always prefer nice logic over nice aesthetics, although both together is obviously better.

Rules for Sudoku

In this Sudoku, clues are given on the outside. Digits on the outside indicate that these digits appear in the 2nd, 3rd or 4th cell in that row or column when looking from that side.

Daily League Sudoku #69: Palindrome Sudoku

I've been intending to post some puzzles on my blog, but that never really seems to happen. I wrote a couple of Sudokus for the Daily League to post in the upcoming weeks. But as the Instruction Booklet of the WSC just came out, I've noticed some of the variants I wrote are useful as practice for the WSC. So I'll be uploading those puzzles earlier than planned. I will try to post a Sudoku and/or puzzle a day as practice for the WSC, but I could be missing a puzzle once in a while.

This first puzzle does not actually appear as a separate variant in the WSC, but the practice might be useful. I enjoyed the opening of this puzzle. The original design had a symmetric layout, but the extra clues somewhat invalidated the created opening, so I reduced the puzzle a bit to make the solve come through more. This is the third Palindrom Sudoku I've written and for some reason the centre of the sequence seems to always end up between R2C3 and R1C4. Clearly this seems like the right point to start a line for me.

Rules for Sudoku

In this Sudoku, the digits along the grey line form a palindromic sequence. This means the digits along the line read the same starting from either end.

Daily League #68: Inside Sudoku and Outside Sudoku

This is the second twin Sudoku. This time it's a combination of Inside and Outside Sudoku. They're pretty similar types, but the solve is still different.

Inside Sudoku first appeared on the US Sudoku Qualification. I thought the idea worked pretty well. I don't remember seeing it anywhere after that. I turned the idea in a Frame Sudoku, which has been repeated numerously, mostly by Richard Stolk.
The construction of the combination took a bit of work. Setting up the opening was pretty easy, but after that it gets a lot trickier. It's hard to pick the right digits that help both puzzles along. I liked the opening and found some points that nicely helped both puzzles along. It was hard to find a way to get both puzzles unique. There were a few situations that wouldn't resolve uniquely and I took a while to figure out how to avoid those.
I think both puzzles turned out nicely. The Outside Sudoku is the easier of the two. You get a lot of simple digits from the opening, while the Inside Sudoku's opening is more of a struggle. Enjoy.

Rules for Sudoku

Inside Sudoku: In this Sudoku digits on the outside indicate that these digits must appear in the 2nd, 3rd or 4th cell in that row or column when looking from that side.

Outside Sudoku: In this Sudoku digits on the outside indicate that these digits must appear in the first three cells in that row or column, when looking from that side.

Click to enlarge

Daily League #67: Edge Sums Sudoku and Frame Sudoku

Possibly this month will feature five Double Trouble Sudokus. I have written two so far, but I don't know if I will be able to write three others in combinations I haven't seen before. But I'm at least going to give it a try.

This week the puzzle can be solved both as an Edge Sums Sudoku and as a Frame Sudoku. I have used them together in a puzzle, but now they're separate puzzles. I tried for a while to get both puzzles to be solvable without any givens. I only had a limited range of sums to work with, which caused some issue. Edge Sums was the hardest to get unique in this combination as Frame Sudoku gives you the option of creating a useful implied sum. Eventually I compromised by putting two givens in the middle. The Edge Sums puzzle is the easier of the two in this set.

Rules for Sudoku

Edge Sums Sudoku:
In this Sudoku numbers on the outside indicate the sum of the first two digits in that row or column, when looking from that side.

Frame Sudoku:
In this Sudoku numbers on the outside indicate the sum of the first three digits in that row or column, when looking from that side.

Click to enlarge

16th 24-Hour Puzzle Championship

The 16th 24-Hour Puzzle Championship was held in Budapest this weekend. As always the championship featured 14 puzzle sets to be solved over 24 hours, with each round lasting 100 minutes, with only 10 or 20 minute breaks in between. Neil Zussman was this year's winner with a slim 10 point lead over Robert Vollmert in second place and a 23 point lead over Michael Mosshammer in third place. Full results can be found here.

All puzzles of this championship (except round 11) can be found here. If you need an example of any of the puzzles, you can find the instruction booklets here.

I provided a set again this year. It was the 8th set to be solved between 11pm and 12:40am. The set contained 24 puzzles. It featured 12 genres, with one puzzle being a standard and one puzzle being a variant. I was originally going to include only 6 genres and two standard puzzles and two variants. I found it hard to decide on the genres to provide enough variation. I tried to keep all variations different per genre, to add to the variation in the round. I think it ended up being a good mix.
Robert Vollmert was the top scorer of the round with 810 points.

Puzzles can be found below

Daily League #66: Round Off Sudoku

This is the last puzzle that was originally written for the Polish Sudoku Championships.

The last puzzle is a Round Off Sudoku. I've solved a number of them, but had never written them. Most of these puzzles were written by Richard. I wanted to give a nice pattern with relatively few cages. I thought the problem would be getting it unique, but at the start I ran into a lot of situations where there was no solution left. When I finally figured out where I was messing it up, it was still a struggle to get it right. I had a few puzzles that turned out a bit too hard, where I didn't think it would fit into a puzzle competition. The opening created a few sticking points I had to avoid, which would easily lead to uniqueness issues that I had no way to fix. This was the puzzle that came out in the end. It shouldn't be too hard. Enjoy.

Rules for Sudoku

In this Sudoku, the grid has a number of marked two cell dotted cages. The two digits in these cages form a two digit number read from left to right. The number in these cages indicates this number rounded off to the nearest multiple of 10. Numbers ending to 1-4 are rounded down, numbers ending in 5-9 are rounded up.

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Daily League #65: Rossini Sudoku

This is the third puzzle that was originally written for the Polish Sudoku Championships.

This week it's a Rossini Sudoku. I was trying to design a puzzle without any givens. But I noticed pretty quickly on that this wasn't as easy as I had hoped. The middle of the grid is a lot less accessible as I had thought in advance. I remember seeing one before without givens, but to achieve that I'll need to set up the middle boxes better than I did now. But as I liked how the opening worked out, I finished the puzzle with a few givens. I am happy how it turned out. Enjoy.

Rules for Sudoku

In this Sudoku arrows on the outside indicate that the first three digits in that row or column, when looking from that side, are in ascending order in the direction of the arrow. All possible arrows are given, so if there's no arrow the digits can't be in ascending order.

Click to enlarge

Daily League #64: Hi-Lo Frame Sudoku

This is the second puzzle that was originally written for the Polish Sudoku Championships.

This week it's a Hi-Lo Frame Sudoku. I like the Hi-Lo concept as it gives a little bit of extra information about the third digit that isn't involved in the sum. I've written a few before, but I haven't used it for the league before. I did combine it with another variant, but it should be fun by itself. I think this is probably the hardest puzzle in the set because it requires finding the right few steps through the opening. I prefer not given all possible clues as otherwise you get a big opening on where either the 1 or 9 goes within a box. In the end the path gets a bit more flexible as you have placed digits to help out. Enjoy.

Rules for Sudoku

In this Sudoku the numbers on the outside indicate the sum of the highest and lowest digit in the first three cells in that row or column when looking from that side.

Click to enlarge

Daily League #63: Clone Sudoku

This month there were four puzzles I wrote for the Polish Sudoku Championships. They weren't needed though. As I hadn't used any of these types for the League, I figured I could use them for that. I wrote these puzzles to fit more in a competition and I expect them to be a bit easier than normal. I can never be 100% sure as I sometimes assume an opening deduction is pretty straightforward, but that doesn't mean it can't be hard to find. I'd love to hear some feedback on whether these puzzles would be suitable for a championship. I haven't written many Sudokus for competition solving.

The first puzzle is a Clone Sudoku. I thought the pattern of givens around the Clone region looked nice. I was hoping to make the pattern work with two empty boxes, but I couldn't get it unique. One extra clue did make it unique. It makes the puzzle asymmetric, but it is still a good solve.

Rules for Sudoku

In this Sudoku, digits in the same place in both grey figures must be identical.

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Daily League #62: Mathrax Sudoku

This is the fourth and last puzzle in the 'Latin Squares Sudoku' series. This week it is a Mathrax Sudoku. Originally I had planned a Kropki Sudoku, but after the GP I wasn't really in the mood of writing one. So instead I opted for a Mathrax Sudoku. This type has been a bit of a nemesis with me but the most recent one I actually managed to solve.

For the design I wanted to make two lines containing each type of clue once. I think it looks pretty nice. I needed two extra clues for uniqueness. It is not really a hard puzzle, especially compared to some other Sudokus on my blog. It should still be fun to solve. Enjoy.

Rules for Sudoku

In this Sudoku some intersections of the grid lines are marked by a number and an operator (+, -, x, /) in a circle. The number is the result of the operation, applied to both pairs of diagonally opposite cells. An "E" in the circle indicates that all four adjacent digits are even, while an "O" indicates that all four adjacent digits are odd.

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Daily League Sudoku #61: Easy As ABCDEF Sudoku

This is the third puzzle in the Latin Squares Sudoku series. This week again a familiar variant. Easy As puzzles are one of the more standard Latin Square puzzles at WPCs.

I always like to write larger Easy As puzzles with numbers as it gives a bit more freedom in designing the puzzles. It's always hard to see whether or not you can get the puzzle in the centre if you can only give the outside clues. I have seen a few larger puzzles with standard clues, but there aren't that many grids that qualify for a unique solution.
I looked for a nice opening for a while. I think this one works pretty well. With the regions it opens up a lot of new openings to try out. I picked the layout of the letters at the start and was trying to keep all number 1, 2 or 3. But in the end I couldn't find a unique solution once I got to the end without using a 4. This didn't really hinder the path of the puzzle much, so I am happy how it turned out. Enjoy.

Rules for Sudoku

Place the letters A, B, C, D, E and F once in every row, column and marked 3x3 area. Clues on the outside indicate the position of that letter in that row or column when looking from that side. E.g. A3 indicates that A is the third letter seen from that side.



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Daily League Sudoku #60: Doppelblock Sudoku

This is the second puzzle in the 'Latin Square Sudoku' Series. I've always liked this genre. Nine by nine puzzle are normally pretty hard to accomplish, but it's possible. Adding the regions makes it much easier to construct.

This variant is pretty similar to Between 1 and 9 Sudoku, except for the fact that you aren't forced to give a given. I tried to use an opening that takes the regions into account. This puzzle shouldn't be too hard. I actually had a harder version of this puzzle, but it was a bit too much in my opinion. I didn't even have an option to make it easier without ruining most of the puzzle. I hope it's fun.

[Edit: Puzzle fixed. I made an error, forgetting 7 could be a single digit sum.]

Rules for Sudoku

In this Sudoku you have to blacken two cells in every row, column and marked 3x3 region. Then you have to place the digits 1~7 once in every row, column and marked 3x3 region. Numbers on the outside indicate the sum of the digits in between the black cells in that row or column.




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