Logic Masters India announces January 2012 Sudoku Test — Shapes and Sizes

Dates : 7^th and 8^th January

Length : 120 minutes

IB and Submission Link : http://logicmastersindia.com/M201201S/

Author : Richard Stolk

Irregular.. eek! Well there goes my rise in the rankings. On the other hand, good practice to improve my irregular sudoku solving capability, if thats indeed possible!

Since I do not have my own website, I consider my user page at Logic Masters Germany (LMD) as my homepage. Every Friday at noon (CET) I publish a puzzle in the puzzle portal. (It is not always a sudoku variant by the way). A lot of these puzzles have instructions in both German and English language. I am still busy to write the English instructions for the remaining puzzles.
I noticed that a lot of the participants in the monthly tests here at LMI are also a regular visitor of LMD. They are familiair with my puzzles. To give everybody the opportunity to get used to my puzzles (apart from the IB), I have prepared a list of links to my puzzles that are the most relevant for the coming test. Please note: Some of these puzzles are more suitable for leisure solving; being too hard to use in a test.

Here is the list (all of these puzzles have proper English instructions):

Plain chaos sudoku:
Easy
Medium
Hard

Chaos windoku:
Very hard
Easy

Twin chaos sudoku:
Very hard

Low-digits chaos sudoku:
Medium

Nonconsecutive chaos sudoku:
Medium

Chaos sudoku with other constraints:
Very easy, odd/even
Medium, diagonals
Hard, consecutive

Scattered sudoku plain:
Medium
Medium

Scattered non consecutive:
Hard
Hard

Scattered sudoku with (outside) sums:
Easy
Medium

Scattered sudokuro:
Medium

Scattered sudoku with other constraints:
Diagonal, hard
Kropki-like, hard
Kropki, hard
Kropki, hard
Kropki, small, easy

Irregular sudokus with added clues:
Medium
Hard
Very hard

Overlapping irregular sudoku:
Hard
Medium, 2010 - 2011 specialty; digits 0,0..7
Hard, Xmas 2010 specialty; replace letters first
Hard

Toroidal/cylindrical plain:
Medium
Medium
Medium
Hard, 0~9

Toroidal with other constraints:
Easy, consecutive
Medium, kropki

Chain sudoku:
Easy

After preparing the test I had a few spare puzzles unused. Those puzzles will be published today in the puzzle portal of LMD. I will provide a link to these puzzles later today.

Have fun with the puzzles!

Best regards, Richard

Edited by Richard 2011-12-30 6:08 PM

As promised earlier, here are the links to the 'Leftover'-puzzles that I published today:

Scattered outside sums
Cylindrical
Chaos windoku
Scattered overlapping

Have fun!

Irregular sudoku: A big challenge for me ! I have great difficulty in being fast on these grids. I face to this problem: trying to increase speed makes me do a lot of mistakes , more than on other variations...

However, I look forward to this test , and have no doubt that it will be very useful for me !

Fred

YEAH !!!!!
First test in NEW YEAR..2012
hope to have good start..
Nice selection of sudokus.. IT's really chaos !!! :)

Thanks Richard for the links to extra practice puzzles.
I've a question. In terms of difficulty, how do you rate the 'leftover' puzzles with respect to the actual puzzles in the test?

Sorry Deb, I forgot to mention that.
All four 'leftover' puzzles are harder than the ones in the real test. That's the reason why I didn't use them in the test.

That's too bad. I really liked the difficulty of 3 of the 4. Only the smallest had me stumped, till I remembered it was your puzzle and I figured I should look in one place and the next step was exactly there. Opposed to Fred i´m a big fan of chaos sudokus. Any sudoku that doesn´t have 3 by 3 regions is preferred by me.

We are making a small change to the image of Sudokuro - the clue cells are made more gray. Here is how the new image looks like.

Updated IB uploaded, but this is the only change.

Is it possible the online solving in this test?

Yes. We'll put all examples online for practicing. May be in next 24 hours.

All examples can now be solved online.

This test has lot of non 9X9 sudokus. So we needed to tweak the flash interface a bit.
Request to online solvers : please report any issues while solving/testing the examples before the test starts. It is unlikely that we'll make any changes after the test starts.

Is it correct, that in Scattered non-consecutive sudoku, 0 and 1 ARE consecutive and 9 and 0 ARE NOT consecutive?

@TiiT: Yes, that is correct.

hey can anyone help me out with scattered non-consecutive sudoku..
just got a "0" at r9c10..
and also with scattered sudoku with added clues...
in this got few numbers like 1 and 2 at few places but not able to proceed further..

Check 13 = 6+7
After that in left grid, R2C2=4
and then R1C1 = 3, R6C4=5
It is really smooth solve, so I guess you are not focusing on all the given sums.

Edit : Wrong steps

Edited by debmohanty 2012-01-05 10:21 AM

how can left grid r2c2 be 4 ?

because it will make r2c2 = 6 in right grid.
that makes r3c3 = 7 and r2c6 =7 in right grid..
which in turn makes r3c3 = 6 and r2c6 = 6 in left grid. This contradicts that grey cells must contain 1-7 only once

i think after concentrating on what u said about 13..
the r2c2 should be 5.
then r1c1 = 3 as you said..

and i cant believe that i got the opening of scattered non-consecutive..IT was really very hard to find it out took literally more than 3-4 hours but got it just now..
thanks for the help.

Since there are not much given digits in the grid and they are concentrated in four areas, one of those areas must provide the start.
After the 0 you found in R9C10 the real start of the puzzle can be found in R1C8 + R1C10. What digits can go there?

Since I am the author, I hesitate to give more detailed answers.

Best regards, Richard

nope
thanks for it
:)

After several attempts, that zero is the only digit I have as well. However, only now, after reading here, do I realize that the puzzle is non-consecutive. That may have been the source of my problem.

So yeah, I should really enter answer keys when i finish a puzzle. after not leaving enough time last sudoku test, this time I just totally forget to put in an answer key of the cylindrical, which was one of the first I finished.

What I observe over many tests is that, many players submit as soon as they are done with a 'page'. So typically 2 puzzles or so.

It was nice test..
Just missed to submit an answer. Only 10sec were left..
I loved to solve the low digits sudoku..
i am happy even though with low score because i solved each puzzle without guessing.
Hope this will improve in next test.

On my Macbook, Preview (version 5.0.3 (504.1)) fails to open the encrypted puzzle booklet. Can anyone else with a Mac confirm this? I've recently reinstalled the OS, so it might be a problem on my end, but I can open the encrypted PDF of this weekend's logic-masters.de contest just fine.

@rob, check your email please.

ETA : rob confirmed that this pdf file works. So if anyone else with Mac faces problem, use this pdf instead.

Edited by debmohanty 2012-01-07 9:59 PM

Wonderful Sudokus there.

On a personal note, probably not a good idea to solve scattered and toroidal sudokus when you're half asleep and all but unfortunately this is the only time I'll be getting this weekend :| Considering that, I'm quite happy with my score for a type I'm weak at.

Will surely go through the rest of them later.

Mine opened the puzzle book just fine - although my version of preview is 5.5.1 (719.11).

I really enjoyed the set - the low digits type is easily my favourite sudoku variation of recent times. I'd be interested to know whether my assumed "logic" for the overlapping puzzle actually does hold in full generality as well...

With no player participating now, Shapes and Sizes is over. A rather difficult Sudoku set to begin the year, but I guess, most players expected that.
janoslaw came close to solving all, but missed the last puzzle with 10 minutes to spare. He takes the 1st position.
deu finished 13 puzzles too, and takes the 2nd position. KrtekHonza is 3rd with some margin from deu.

Rohan, Rakesh and Prasanna take the top Indian spots.

A total of 192 players, out of which 151 players got 0+ scores. Thank you everyone for participating.

Thanks Richard for the challenging set of puzzles. Please share your thoughts on your first LMI test.

Link to solutions

Here are my thoughts:

Let me start telling that I was very honored when Deb asked me if I was interested to write a sudoku test for LMI, especially when I noticed the majority of the world top players participates every month. I had a few doubts, because so far I have only contributed my puzzles to championships, leaving it to the organiser which puzzles can be used and which not. Now it was up to me to do the whole lot: creating the puzzles, deciding how the set is assembled, the points distribution and the solution codes.
One of my major problems is that I am not among the worlds best solvers. I consider myself somewhere in the Dutch subtop, but that’s it. This gave me a hard time on deciding how hard the test had to be and how much puzzles it should contain. Fortunately every potential pre-tester I asked to help me testing responded positive to my request, so I had a lot of feedback from them. Three of the testers ended in places 40~50 at the last WSC. After the testing I thougt it would be just possible for the World top to finish all 14 puzzles, or it would be very close. The latter became true. Congratulations to janoslaw, deu and KrtekHonza!

I am very fond of irregular grids. I think they are not often enough in magazines or contests. (Or are they just not popular enough by puzzlers?) For that reason I was very eager to make this test with all irregular grids. I realise that irregular grids might scare off people, because these grids are more error-sensible while solving. I hope the popularity of irregular grids didn’t drop during the test! :) At least I am happy that nearly 200 players participated, and that about 25% did not submit any solution does not surprise me either.

Quite a lot of people submitted only 1, 2 or 3 solutions. All in all I think I can conlude this test was a little bit too hard. Nevertheless I hope you had fun with it. I really enjoyed creating the puzzles, and also looking behind the screens this weekend to see the players making progress. ;)

Once again I would like to thank LMI for the opportunity to write the test and all participants for taking part!

I hope to read how you all liked it.

A very good set of Sudokus. Though I am not good at solving regular Sudoku's, at first I thought of not giving the test, but since this is the first test of 2012 I decided to give, now I am saying that I am looking forward for another one.
I had a lot of trouble in starting off with the Toroidal Sudoku, even though it is the one with lowest points (which I think is an easier one), then I left it and went for Toroidal in Large Grid and it went smoothly and finally caught the trick in Toroidal sudoku to complete it.
I liked Toroidal concept a lot.

Thanks to Richard and LMI for the wonderful contest.

Regards,
Ravi

Is it possible to color the chains in Chain Sudoku for the future tests?
I had a lot of trouble in solving the example and could not keep track of chains, but the test was already started and I do not want to raise any unnecessary concerns.
I also see that no one has raised this concern, so is it something only I had trouble with or do I need to follow any rule or something to work with these kind of variations ?

Please let me know.

Regards,
Ravi

Using colors other than shades of grey is not allowed in LMI tests. Not everyone has access to color printer.

Players who solved Chain Sudoku should be able to tell you how they kept track of chains.

I found the entire set highly enjoyable. Specially liked scattered non-consecutiive and Cylindrical. This is coming from someone who generally hates Irregular Sudokus. :P

It was a tough set. Initially, I was just switching from one sudoku to another, trying to get something sturdy going. Luckily, I was able to return and finish off all my half-solves except non-consecutive. Can someone solve the first few numbers (around 8-10) logically?

Talking about favourite sudokus, Low Digits was incredible. It was like 'Wow, this can't get better' after I solved it. It was beautiful. No wonder it's average rating is 9.5 from 10 votes.

I avoided the Toroidals for as long as I could, but eventually, I ran out of choices. I wasted some time on Windoku and Non-Consecutive, and missed out on the latter. But, overall, its been a good start of the year. Lets hope it gets better with every test.

Thanks for the test Richard. I'm sure many players would improve in Irregular variants after this test.

I didn't solve it during the test, but I did it quite quickly later considering the points value. My initial steps included getting the possibilities for the 0s, the 2s, getting the 2 diagonally touching 1s in the two middle rows, and figuring out that there have to be 2 1s in either of the boxes at R2C2,R9C2,R2C9,R9C9. My first digits entered were mostly using the middle regions and not the corner regions though, and mainly I could narrow it down a lot in the middle bottom region. I guess you'll be able to do that since thats the least confusing part and all the extra cells are clustered away from the middle regions.

I will post the first part of the walkthrough for this mean puzzle tonight, when I am home.
It is the highest points puzzle, compared to size, which is the reason that it has a bit of a tough start.

OK Here it is: R5C5 = 1 R6C6 = 1 R8+R10C5 = 07 7 in C2 locked in R1 or R3 R5C3 = 7 R8+R10C6 = 29 R7C6 + R6C7 = 35 6 in R6 locked in C135 R6C5 = 6 R5C1 = 5 R7C5 = 3 R7C6 = 5 R6C7 = 3 R6C10 = 2 R6C8 = 5 R6C3 = 0 R3C5 = 2 From here it should run smoothly.

I noticed the very high rating. Although I am very happy with the ratings of all puzzles, I wonder why especially this one is by far the highest. Is it the shapes of the irregular areas? Or the straight forward solving path? I am very fond of symmetry, in shapes, grey cells and patterns of given digits. The fun part is that this is the only puzzle where symmetry is not possible in the grey cells.