Daily League Sudoku #43: Next To Nine Sudoku

Last Tuesday was the Dutch Sudoku Championship. I won the Dutch Championship and can now call myself Dutch Sudoku Champion for a year. The puzzles can be found at http://wcpn.nl. All Sudokus were written by Richard Stolk. In case you need the English translations for the instructions, they can be found in this forum post. This Sudoku was one of the types appearing the championship. I thought this was most likely the least common type to appear in the test, so that's why I decided to write one myself.
I think this puzzle isn't too hard, but I will await the times to see if my judgement is accurate. They are more often not correct when it comes to Sudokus. You can solve the puzzle at SudokuCup, which features all Daily League Sudokus suitable for the applet on a one day delay.

Rules for Sudoku

In this Sudoku, the digits on the outside indicate which digits are directly adjacent to the digit 9 in that row or column. The digits are not necessarily listed in order.

Click to enlarge

Daily League Sudoku #42: Hit Sudoku

Last weekend was the Japanese NumberPlace Championship. It was full of great puzzles, but my favourite was the Hit NumberPlace by Naoki Inaba. I didn't manage to solve it during the championship as I didn't find the logic. But once I found the logic afterwards I really enjoyed it. That's why I decided to write one of my own for the league.

During the solve I realised a bit of logic that I thought would be fun to use in one of these puzzles. I just had to find a nice solution grid in which I could easily implement this. I actually stole a solution grid from the JNPC, which I slightly altered as at one point during construction I ran into no solution. But I noticed that by switching a few numbers around it could still have a solution. The trick I used isn't overly hard but I think it might be wise to try to solve the original puzzle first so that you can understand the logic involved, because I think it is useful to understand the genre before attempting this puzzle. The hit NumberPlace is #19 in the set.

That said, the puzzle is completely logically solvable. I think it is nice but it a bit on the harder side. Still, I hope you'll enjoy it.

Rules for Sudoku

Numbers outside the original grid indicate how many digits are the same in the solution grid in the corresponding row or column.

Click to enlarge

Daily League Sudoku #41: Pusula

I haven't written any Sudokus in a while. Now that Tom Collyer is taking a break to focus all his attention on the upcoming World Sudoku Championships in the UK, I'm taking over the Friday together with Zoltan Horvath. We'll probably be alternating weeks, so that we both get our fair share of puzzles in.

I got this type off Serkan Yurekli's blog. I was browsing it for an example of a puzzle type and came across it. I thought it would be a nice idea for the Daily League. I hadn't ever made one. It wasn't too hard to write this type. I think in general many grids will allow a unique solution, but there's a few restrictions to the solution to make that viable. I wrote this one progressively and added the missing arrows in the end. I don't think it's necessary to follow the intended solving path as there's a general strategy to this puzzles that should also always work to solve them. I hope it's enjoyable. It shouldn't be overly hard as some of my other Sudokus have been.

Rules for Sudoku

In this Sudoku an arrow in a cell with an even digit points to the largest odd orthogonal neighbour of that cell. An arrow in a cell with an odd digit points to the largest even orthogonal neighbour of that cell. All arrows have been given.

Polish Puzzle Championships 2014: Team Round

This post will contain the puzzles I provided for the Team Round of the Polish Puzzle Championships. It wasn't an official round but a fun thing to do during the evening. Zoltan Horvath had contacted me if I had time to help working on a team round. as I had just finished my individual round, I figured I could. Zoltan came up with the idea of a Puzzle Labyrinth, where you needed to find your way through the labyrinth by solving puzzles and getting a clue to which would be a next puzzle. Eventually this evolved into a labyrinth where the puzzles were missing from the labyrinth and you had to place them back in the labyrinth. We decided to split the puzzles up into four categories, which would be marked in the empty labyrinth.
On Zoltan's suggestion we gave eachother 8 puzzle types, 2 per category, to write and we could choose one puzzle type ourselves. I gave Zoltan Tapa, Yajilin, Thermometers, Haido, LITS, Regional Akari, Yin Yang and Crossing Loop to write. He chose Lighthouses, First Seen Corral, Loop Extra and L-Dissection to write. He gave me Cave/Corral, Number Sea, Grades, Catloop, Retrograde Battleships, Star Battle, Masyu and Penta Blokus to write. I chose to write Kurotto, Laser, Tetromino Areas and Finnish Snake. Most puzzles had no restrictions, except that they shouldn't be too hard. Only the Circles puzzles had the restriction of being monocoloured. This was only a problem for Yin Yang and Masyu as those normally have multiple coloured circles. The Masyu worked pretty well, but Zoltan's Yin Yang topped that way more in difficulty to create. I was impressed with his puzzle. It was fun to solve. He wrote another harder one too.
When the puzzles were done we had to create a labyrinth. I first wrote one where each puzzle gives you one clue. But that labyrinth turned out too hard, so Zoltan rewrote the labyrinth with two clues per puzzle. This way it was easier to solve.
During competition most teams managed to solve the whole labyrinth, with the quickest doing it within 30 minutes.
You can find the Team Round in the following link.

Besides the Team Round, I will be also adding my harder labyrinth for those who like the challenge. You will have 3 options.
You can choose to solve this first file. [Edit: File updated 19-04-12014 5:25am blog time] It contains all puzzles with correct and incorrect clues. You'll need to solve the puzzles to figure out the correct clues and then use those correct clues to place all the puzzles in the grid.
You can choose to solve this second file. It contains all the correct clues only and no puzzles. It also contains a logical opening on page 3 and the solution on page 4. You can also use this after you get stuck on the first file or to check I didn't make a mistake when setting up the first file.
Lastly you can choose to ignore this challenge and just solve the puzzles or maybe solve the original Team Round with the easier clues.
It's up to you.

Puzzles can be found below. Sorry about the arrows, but didn't feel like redrawing the images for the blog.

Polish Puzzle Championships 2014: Individual Round

Last weekend were the Polish Sudoku and Puzzle Championships. The Championship was also open to International solvers this year. The playoffs would feature the best 4 solvers, while having at least two Polish solvers.
The Sudoku playoffs featured Tiit Vunk, Jakub Ondrousek, Jan Mrozowski and Krystian Swiderski. Jakub Ondrousek finish first in the playoffs, followed by Krystian Swiderski, Tiit Vunk and Jan Mrozowski, making Krystian Swiderski the new Polish Sudoku champion. Full results can be found here.
The Puzzle playoffs featured Przemysław Dębiak, Matus Demiger, Zoltan Horvath and Tomasz Stróżak. The final results remained almost the same with Przemyslaw Dębiak finishing first, followed by Zoltan Horvath, Matus Demiger and Tomasz Stróżak. Full results can be found here.

I contributed a set for the Puzzle Championships for the individual round and wrote a team round together with Zoltan Horvath.

You can find all puzzles of the Championships in the following link: Sudoku Rounds + Team Round, Puzzle Rounds. My puzzle set is round 4. This post will feature all the puzzles from my individual round. Tomorrow I will post the Team round puzzles with a special surprise.

Last year's set was a bit on the difficult side, so I tried to think of a way to rectify that this year. I decided to write 2 puzzles per type, one smaller/easier one and a larger/harder one. I didn't want to make any too difficult. I selected 10 varying types of puzzles. I was hoping to average about 1.5 minutes per puzzle on the smaller ones and about 4.5 minutes per puzzle on the larger ones. I had the set tested by Prasanna Seshadri, James McGowan and Stefan Gaspar. The smaller puzzles made that average pretty well, but the larger puzzles were more inching towards 5-5.5 average and all of them had some outliers. I couldn't really decide well which puzzles to cut so I sent in the whole set and let them know that they could leave out a puzzle type if necessary. During their testing 3 of the larger puzzles seem to have cause some problems as they went up in score. I think the set will have worked well none-the-less for all solvers with the easier puzzles to work with as well, but I'd love to hear some feedback form those who were there.

Puzzles can be found below.

Puzzle #167: Araf, Nurikabe, Capsules, Catloop

Last weekend were the Polish Sudoku and Puzzle Championships. I wrote a set of puzzles for the championships and helped create a team round with Zoltan Horvath. Today I will be posting the puzzles that didn't make it to the championships. Most of them were too hard for their intended purposes. I will also be posting the puzzles that appeared on the championships later this week.
Three of the puzzle types were from the individual rounds and one is from the team rounds.

The Araf puzzles were the first ones I had written of this type. I still had to get used to construction a bit. When I do that I tend to make the puzzles a bit harder, just to see what's possible. The smaller one isn't too hard, but still a bit harder than intended.
The Nurikabe puzzle isn't actually very hard, but I changed it as I saw an aesthetically nicer version of this puzzle. That one was also a bit easier than this puzzle, which I didn't mind.
The Capsules puzzle was really too hard. It was the first puzzle I'd written for the championships and I hadn't totally finalised my intentions then and thus went a bit overboard on difficulty.
The Catloop puzzle was written for the team round. It is a silly name play on the Catwalk puzzles, which was again a renaming of the Meander puzzle type to give a fun visual theming on the website. I think this type is also known under many other names. The first puzzle is an easy puzzle, while the second is a hard puzzle. I had written the second one first and after feed back written two easier puzzles. One of them went to the team round and the other one was left over. I think this was actually the easier of the two puzzles.

Puzzles can be found below.

Rules: Catloop

Draw a single closed loop through the grid by connecting the centres of cells horizontally and vertically. Numbers on the outside indicate how many cells are used by the loop in that row or column.

This puzzle is a variant on Catwalk. In this puzzle type you draw a path from the given beginning and end point instead of a loop.

Rules: Araf

Divide the grid into some regions, formed by orthogonally adjacent squares. Each region should contain exactly two given numbers. The size of each region should be a value (in unit squares) strictly between the two numbers inside that region. Its size can't be equal to either of the numbers in the region.

14th 24 Hour Puzzle Championship

This year I wrote a set of puzzles together with Hns Eendebak. I was a bit tight on time with a holiday and other championships that I wasn't sure if I'd be able to write everything in time. I still ran a bit late getting everything together but it was in time for the championship.
This year's championship was won by Peter Hudak. Nikola Zivanovic and Zoltan Horvath finished second and third.
There were 30 competitors total in this year's championship, of which 29 did our set. The set was a bit on the long side this year with the Michael Mosshammer from Austria being the top scorer with 695 points. It would have been better if the top scorer had about 100-150 points more. The set contained 24 puzzles in total, so I should have probably cut 2 puzzles in the end.
In this post I will be adding all the puzzles I wrote. You can find the complete set and all other sets here. If you need to see the instruction booklets for any of the set you can find them in this forum post.

Puzzles can be found below.

Puzzle #166: Domino Extra

The last puzzle are two Domino Extra puzzles. I'd written two at the start, but they ended up testing too hard. So I wrote a third one that was much easier than these ones to be included in the WPC set. They have a similar opening, but should both still be fun to solve.

Rules:

Divide the grid along the grid lines so that each given pair of numbers appears in exactly one shape.

 

Puzzle #165: Blind Spot

Today the second puzzle that wasn't used in the WPC. This is a Blind Spot puzzle. It's actually a size smaller than the puzzle used at the WPC, which was 7x7. But I actually think this was the harder of the two puzzles. That's why the larger puzzle was used in the WPC. I like writing these puzzles, but I think they can be tricky to solve as the logic is a bit unfamiliar compared to other Latin square type puzzles.

Rules for Blind Spot

Puzzle #164: Gemini Loop

I was going through my puzzle files and realised I had a few unused puzzles that I had written for the WPC 2013. One of each type was used, but for certain types I'd written a few just to have a choice depending on how they tested. I had posted two sets of puzzles before, that I had originally written for the WPC, but these puzzle types were rejected. These puzzles were the following Yajilin and Pentopia puzzles.
Today's puzzle is a Gemini Loop puzzle. I think it's a nice puzzle but I selected the other one for the WPC as I thought that one solved a bit nicer.

Rules:

Draw a single closed loop through all squares in the grid by connecting them horizontally and
vertically. The loop doesn't touch or cross itself. Cells with the same letter all have the same
appearance as to how the loop passes through it. Cells with different letters have a different appearance.

Puzzle Competitions: ZeKa 2014

Last weekend was the ZeKa competition in Croatia. It featured both a individual and a team competition this year. The individual competition was won by Goran Vodopija; Marko Obradović and Dragan Tolomanoski finished second and third respectively . The team competition was won by Dragan Tolomanoski, Bojana Vojnović and Vanja Fornazar.
I provided one of the Team rounds this time. The theme of the round was Imposters. The round consisted of four classic puzzle types. Each type had 4 puzzles, where one of the puzzles was an Imposter. It wasn't actually solvable as that puzzle type, but was solvable under a different set of rules. The rules of this puzzle was provided. The imposters weren't designed to be logically deduced, but purely intended to break down under the original rules.
The four puzzle types were LITS, with Double Back as imposter; Shikaku, with Corral as imposter; Skyscrapers with Haido as imposter; Slitherlink, with Turning Fences as imposter. Two of these combinations have appeared on my blog as a Double Trouble puzzle. One of them appeared as such on Grant Fikes' blog. The other is probably possible as a Double Trouble puzzle, but haven't tried that yet.

Puzzles can be found below or in the following PDF.

Rules: Shikaku

Divide the grid in a number of non-overlapping rectangles along the grid lines. Numbers in the grid indicate the size of the rectangle they are in. No rectangle can contain more than one number.

 

 

Puzzle #163: Turning Fences

The LMI Marathon puzzle that was solved during the competition was actually the second version. In the first version I put in some stuff that came naturally to me for this genre, but stumped the test solvers. That's why there was an easier second version, which still took a relatively long time for the test solvers. That was why I added the Tutorial on my blog, just so people would realise the basics that I had figured out when designing these puzzles.
Here is the first puzzle I wrote. There are a few similarities to the second puzzle as I kept the bits that were solved quickly in the first test solve in the puzzle. It has the same layout as the second puzzle. For those who hadn't figured out the layout, the givens are in the shape of 25 letters that spell out TURNING FENCES LMI MARATHON 3 in an inward clockwise spiral. The 3 shape is made up completely of 3's.

Enjoy, but take some time to get through it logically.

Rules for Turning Fences

Click to enlarge

Tutorial: Turning Fences

This week the LMI Puzzle Marathon will start. It will run from February 21st till March 2nd. For this event I have written a Turning Fences puzzle. To prepare people a bit for a more unknown genre, I will write a tutorial about the logic behind the genre. It won't be complete, but it should be enough to tackle the upcoming puzzle. In the next days there will also be a few practise puzzles. You can also practise some of the puzzles already on my blog, but most of these are logically harder than the puzzle in the actual test. For those who happen to own Akil Oyunlari Issue #75, there are also 4 of these puzzles by my hand in there. They are logically a bit more friendly.

Tutorial below.

Daily League Sudoku #40: Inside Skyscraper Sudoku

Today's puzzle is a Skyscraper Sudoku variant. This is a more Logic Puzzle variant of Sudoku. I normally would represent this as a Regional variant of Skyscraper puzzles. The Sudoku part doesn't often come forward as much as the Skyscraper part during the solve. But as I always like Skyscraper Sudokus, I figured I'd make one too. This variant sometimes has all possible arrows given, but I prefer it without this rule. A lot of the smaller numbers end up being unnecessarily given an arrow there, although the negative information is also fun to use. I just prefer it this way.
I had set up this opening a few weeks ago, but I was not able to finish the puzzle successfully. After a few more tries, I came up with this puzzle. I was originally intending to make the clue arrangement symmetric, but as you can't just put a clue everywhere that caused some problems. This was the point where the puzzle ended up being unique. I liked the way it solved at the end, with a somewhat tricky step to finish the puzzle. So that's why I settled for this one. I had a little trouble finding a satisfying layout, but I think this one should do. If someone has a suggestion that could work better, I might change the image. Having said that, enjoy the puzzle.

Rules for Sudoku

In this Sudoku each digit indicates the height of a Skyscraper. Digits in cells with arrows indicate the number of buildings that can be seen in the direction of the arrow from that cell. Taller buildings block the view of smaller buildings.

Daily League Sudoku #39: Palindrome Killer Sudoku

Today's Sudoku is themed around today's date. As the date is a palindrome, the choice of Sudoku was easy. I chose for the combination with Killer Sudoku as I could use 21 and 12 easily in that variant.
The puzzle has a somewhat complicated opening. But I hope that people will understand where to look considering the choice of combined variants. If not, I guess there's very little to get in this one. But when the opening's finished, the solve should solve without much problems.I'm still happy with the Sudoku overall. I think the 21/12 layout of cages looks really nice and the way the palindrome resolves the obvious non-uniqueness worked out really well. I hope people will feel the same. Enjoy.

Rules for Sudoku

Instead of given numbers, you now have a few dashed cages. The number in a cage indicates the sum of the digits in the cage. Digits can't be repeated in any dashed cage. Additionally, digits along a grey line must form a palindromic sequence.

Click to enlarge

Daily League Sudoku #38: Parity Count Sudoku

This week's Sudoku is an Odd/Even Sudoku variant. I'm pretty sure I have seen this idea before. I have no idea where or what is was called then. So I just gave it my own name.
I always like Sudokus that use parity constraints, which require you to basically build an Odd/Even Sudoku. I made a puzzle that required this before, namely my Battenburg Sudoku. In this one you actually have to solve the Sudoku to set up the whole Odd/Even Sudoku grid. I think because of the interaction between Sudoku and parity rule, this idea is a bit more interesting. I don't think the puzzle is overly difficult. The opening shouldn't be too hard, but there's a few sticking points in the middle in figuring out which numbers go in certain grey cells. I had fun designing it. I sacrificed symmetry a bit as the left top square being grey helped make it unique and I preferred that over giving extra givens. I hope people enjoy it.

Rules for Sudoku

In this Sudoku digits in grey cells indicate how many digits of the opposite parity appear in the cells touching it.

Daily League Sudoku #37: Non-Consecutive Sudoku

This week again something familiar. I had a different puzzle ready, but I sadly realised my intended opening made no sense. I had adjusted two digits, which I thought didn't affect the opening, but on a resolve I realised they did. I will give that one another go later, but I didn't really have the time to fix it today. So instead here is a Non-Consecutive Sudoku.
I always enjoy solving Non-Consecutive Sudokus. I think writing them is a lot trickier though. I think it doesn't really suit the way I like to write Sudokus or puzzles in general. I think the puzzle solves nicely, but it won't be one of my more memorable Sudokus. But as I promised a more easy Sudoku this week, I think this one will at least keep that promise. Enjoy :).

Rules for Sudoku

In this Sudoku consecutive digits can't be orthogonally adjacent.