Logic Masters India announces October 2011 Sudoku Test — Sudoku A or B

Dates : 1^st and 2^nd October

Length : 120 minutes

IB and Submission Link : http://logicmastersindia.com/M201110S/

Author : Deb Mohanty

This looks wonderful. I can't wait to try the puzzles of the IB... but I will have to, since USSC is about to start. Damn !

ditto

looks wonderful and challenging!!!

There are 12 examples, but around 20 rules. So, there are some 'unused' rules in the IB.
Here are some links which can used for practice. Most of the Sudokus have appeared in LMI tests earlier.
Rohan's blog has examples for many of them as well. If someone wants online solving, check argio-logic.net

Sudoku Type	LMI test link	Rohan's blog link	argio-logic link
Odd Sudoku	ISC2011 finals	search/label/Odd%20Sudoku
Extra Region Sudoku	ISC2011 Qualifier, Fivefold, Spring	search/label/Extra%20Region%20Sudoku
Even Sudoku	Mock18 IB	search/label/Even%20Sudoku
Greater Sudoku	Sudoku Hotpot
Sequence Sudoku	Mock19	search/label/Sequence%20Sudoku
Palindrome Sudoku	ISC2010	search/label/Palindrome%20Sudoku	palindromo
Marked Quadro	Mastermind Twins
Multiplication Table	ISC2011 finals	search/label/Multiplication%20Table%20Sudoku
Neighbouring Sudoku			neighbours
Touchy Sudoku	Mock12, Classic Lookalikes	rules-of-touchy-sudoku.html	Touchy
Anti-Knight Sudoku	Classic Lookalikes	search/label/Anti%20Knight%20Sudoku	knight
XV Sudoku	ISC2011 Qualifier	search/label/XV%20Sudoku	xv
Kropki Sudoku	LOGIDOKU	search/label/Kropki%20Sudoku	kropkinew
Consecutive Sudoku	ISC2011 Qualifier, Spring	search/label/Consecutive%20Sudoku	consecutivo
Fiver Sudoku	Qixi Festival (Give me 5)
Skyscraper Sudoku	Sudoku City :-)	search/label/Skyscraper%20Sudoku	skyscraper
Outside Sudoku	ISC2011 Qualifier, Fivefold	search/label/Outside%20Sudoku	outside
Odd Even View Sudoku	ISC2011 Finals		evenoddview

Point changes for XV/Kropki, Consecutive/Fiver - Updated IB uploaded.

JUST WANTED TO KNOW WHETHER WE CAN APPLY UNIQUENESS TEST FOR THE PUZZLES. IN THE 3RD EXAMPLE OF EVEN/SMALL NEIGHBOUR I CAME ACROSS SUCH SITUATION IN CELLS R2C1 R2C2 , R4C1 R4C2. I WASNT SURE WHETHER THE UNIQUENESS PRINCIPLE COULD BE APPLIED OR NOT. LATER AFTER SOLVING I FELT THAT IT COULD HAVE BEEN APPLIED. PLEASE CLARIFY

The general rule about uniqueness and variants is that you can apply it as long as no cell amongst the ones you are dealing with can be affected by the additional rule(s) of this variant. I can't say more about this particular puzzle but I advise you to be very careful when applying unicity to variants.

Well, I just solved the puzzle but never got in the situation you describe, so I will just examine an hypothetical case. Let's say (all this happening before you determine which is the correct rule) you have R2C1/R2C2=39 and R4C1/R4C2=359. It is tempting to say that either R4C1 or R4C2 contains a 5, but it is a wrong assertion. Indeed, there is one cell (R2C1) which can be affected by the "small neighbours" rule, so you could perfectly have a unique rectangle 39/39/39/39. If it happens that the rule is the one of "small neighbours", then there cannot be a 9 in R2C1 and the unique rectangle is broken.

I hope I made it clear enough, I wrote this a bit in a hurry.

Thanks Bastien for clarifying. Even I didn't catch the situation Akash is describing.

As-is, it is little dangerous to apply unique rectangle to variants. In this test with 2-rules, it is probably little early if you apply unique rectangle before 'determining' the correct rule.

@Akash, to specifically answer if you can apply uniqueness rule, all I can say is all sudokus are designed to have unique solutions :-)

One side note on examples : the difficulty of examples vary a lot, and has nothing to do with difficulty of actual puzzles

With Sum10/Multiple, are all black marks given?
I.e., is it possible in Sum10 that two neighboring numbers sum up to 10 and have no black square between them?
Is it possible for Multiple Sudoku that two neighboring numbers are a multiple of each others but have no black square between them?

All black marks are not given. So converse rule does not apply.

Edited by debmohanty 2011-09-25 11:44 PM

@deb and bastien. thanks a lot for clarifying my doubts.

Is there a double solution in Greater/Lesser sudoku in Instruction Booklet? 7's & 8's in Box 6, 8 and 9.

Not for me because of the 7 between L8C3 et L8C4.

OH ok, now I understand the rules. I think. I got it wrong first. I should always read all the rules more carefully.

All examples can now be solved online in the submission page ( http://logicmastersindia.com/M201110S/ )

While testing the sudokus, Rakesh asked me if it is allowed make 2 copies of the booklet. I didn't answer his question, but I think he printed only a single copy.
There is discussion in sudokuvariante forum that one of the strategy could be printing 2 copies, and solving using different rules on separate copies.

The reasons I'm bringing it up here is
1) I want to make sure that everyone knows that this is a strategy that some player might want to follow
2) More importantly, I feel, just like an offline competition where only one set of printout is allowed, one should use only one set of printout for this test.
3) Most importantly, without revealing much about what to expect in actual sudokus, I can say that printing two copies will not help one solving faster.

Edited by debmohanty 2011-09-28 7:54 PM

Announcements

1) Bonus points

Players submitting all 12 correctly will get .9 points per minute
Players submitting all 12, but 1 incorrect with maximum 3 incorrect digits will get .6 points per minute saved.
As usual, bonus points will be computed from the time "Claim Bonus" is clicked.
So, click on "Claim Bonus" as soon as you think you are done.

2) Sudoku Booklet

Password protected sudoku booklet is uploaded.
It has 6 pages. Each page has 2 sudokus. There is no cover page / points table.

3) Read the instruction booklet carefully

There are more rules than a usual sudoku test has. So please read the IB carefully.
Converse rules doesn't apply to all Sudokus.
Please ask here in case of doubts

4) Score page

As usual, the link to score page is : http://logicmastersindia.com/M201110S/score.asp
The score page will not show bonus points until the test is over

I read this on Hideaki Jo's blog first. I'm not sure I understood well, because I'm not a specialist of japanese translation . I thought it was an interesting point, so I report this on my forum. Thanks for clarifying (and for reading sudokuvariante ) !

Fred

Precisely the same reason I posted in this forum :-) and my French is probably as good as your Japanese

Edited by debmohanty 2011-10-01 6:47 AM

Attention :
If you are solving online, you need not submit again using paper mode. It consumes time and error prone.

Excellent puzzles. Thanks for the fun test!

Deb - Really well done, nice set of puzzles. Enjoyed it! Cheers, Dave

Really nice and very beautiful puzzles Deb!
I enjoyed
- the grids themselves and
- the solving
both very much!

Thanks

Wonderful as expected................Thanks a lot Deb for making me enjoy the weekend

Really nice puzzles. Was just probably 10 seconds away from completing an LMI test for the first time. Ah well guess I'll have to wait longer :P But really enjoyed it.

Big fan of this variant test. Not a fan of killer sudokus, or non-9x9's in contests. When you stay within the constraints of the usual and just add little extra constraints you can rely on all your standard sudoku techniques and just look for the extra direction. First time I have ever bonused on LMI, so very happy about that as well.

Love this site and appreciate all the time that you put in constantly to keep me and all the other world puzzlers entertained.

Much thanks.

TheSubro

The puzzles are very well designed. Thanks a lot Deb.
Though I am not a fan of sudoku I enjoyed the test a lot.
I liked one thing about the test i.e the two variants concept, in usual tests each sudoku is of only one type but in this I guess almost all the variants are covered in such a way, that to solve you need to know both the variants mentioned for each sudoku, thus making everyone to learn more than one variant (atleast in my case) :)

Thanks
Ravi.

Very enjoyable test, although can I put a request in for 6 extra points? I finished the Sequence/Palindrome puzzle early on in the test, but I noticed I hadn't input the answer when I was checking everything at the end. I hurriedly input the answer key and pressed 'submit' with about 6 seconds remaining but I was told that I couldn't submit as the test was over. It hardly makes a difference to my position but at least I will feel my time solving that puzzle wasn't wasted!

Thanks

Rodders

Sudoku A or B is now over. Thank you everyone for taking time to participate. Hope you enjoyed the easy set.

Top 3 : motris (76:04), TiiT (76:16), Fred76 (84:12)
17 other players completed all sudokus correctly before time. Congratulations everyone.

LMI sudokus tests have been bit hard in last few months. Here are the number of players completing all sudokus in last 5 months - May : 0, Jun : 1, Jul : 0, Aug : 0, Sep : 0. So I decided to keep this test bit longer than needed so that many players get a chance to try and complete all sudokus. I am really happy to see that apart from the regular ones, many new players have completed the set.

About the Sudokus : Apart from Odd Even View / Outside view, most sudokus were easy. I think it was possible to find the logic to determine the correct rule for each sudoku. I'm glad that everyone generally liked the concept of A/B, but I felt I could have used more interlinking uses of the rules in some cases to make the grids more interesting. I'm not sure if I could have achieved that without raising the difficulty level. All I can say is, I'm really tempted to write "Sudoku C or D" sometime in the future.

Some stats :
# of participants : 204
# of Non zero scores : 170
# of players submitting all sudokus : 29
# of players getting all sudokus correct : 20
Average time for the 20 players : 102 minutes

3 best buddies get India top 3 positions : Rohan(97:28), Pras and Tejal.

Many thanks to Branko and Rakesh for pre testing the Sudokus. Branko's timing were especially impressive.

Thanks to David Millar for creating the logo.

Looking forward to C or D :D

The fun on the 'A or B' style of solving is to first solve the grid as a normal classic, get as many numbers as possible, and then try to find a contradiction in one of the rules, rather than choosing one and solving until you go wrong or reach the solution. Most of the sudokus were so neatly made. Even/Neighbours and Quadro/MultiTable were phenomenal!

C or D definitely on the cards.

I found half of the grids tough while test solving. However, finding the right variant was mostly easy and elegant.

Looked at the score and noticed that the ratings (as of now) hover between 7.46 and 8.25 for all sudokus - which effectively means that the grids had consistent quality about them and almost all sudokus were highly rated by at least some competitors. Probably this test has the lowest standard deviation ever across grids.

That is a close observation, and you are certainly right that standard deviation is lowest here. Here is top 5 tests with low standard deviations (after we introduced 10-pointer ratings)



Another stat of minor importance : Marked Quadro / Multiplication Table is the first puzzle to be submitted by more than 100 players (125 to be precise), still being 100% correct. The next best was Skyscrapers sudoku (Small) in Logidoku by 81 players.

It looks like you are very strong when you read the rules carefully . You were very close to win a monthly test ! I hope you'll not read WSC' instructions booklet carefully

Thanks for the fun test. Deb, you have accustomed us to magnificent grids, it was still the case this time.
Since November 2010, I had not made such a performance on LMI monthly test. It's very encouraging for next month, even if the truth of the day is not the truth of next day.

Fred

Thanks Fred! It was great test for me, because I didn't do mistakes (like sometimes happens). Also I was able to find the correct rules and solve them without any longer pauses, so It went quickly for me. Only puzzle, I was a bit troubled, was the last one (I'd have liked outside much more), but It was the hardest one in this test anyway. Congrats to you too, Fred, and Thomas, ofcourse. This result means much to me.

Tiit

Deb! Fabulous Test!!! :)
Thoroughly enjoyed solving it, just missed completing an LMI test, was acheivable.

Thanks Deb, that was fun. Even though I made 2 mistakes.

My mistake for puzzle #2 was really dumb though and a bit miraculous. I determined the right rules quickly with the {45} pair in R12C1. Except somehow I continued solving with the opposite rule. And the puzzle also solves uniquely with that rule besides of course that {45} pair. I'm not sure if you were aware of this occurence, but it was somewhat a shocker to find out i got it wrong, till I realised what had happened. then it was more amazement that the puzzle still solved that way.

It was such an easy puzzle, but you and aldentea submitted identical wrong solutions. Both being top players, I kept wondering what could be the problem, but never figured out.
No, I didn't know that it can be solved the other way except that 4/5 pair.

That is just the same as what happened on me!
I'm glad that there exists another player who made such a CRAZY mistake.

Funny mistake !

It should have been worse for you if this "special rule" sudoku had been more difficult. I solve it with this "special rule" and I think the difficulty is roughly the same as the one with original rule.

Thanks Deb, this was really good and, in particular, extremely fun.

A fifth place is rather satisfying considering the number of stupidities I made - and will really have to avoid in one month :

1) trying to solve the Touchy as an Untouch,
2) not noticing that the "2" clue was not the only one on the Skyscraper,
3) spending 30' on the last puzzle ! I guess I was just a bit stressed after having solved the first 11 in less than an hour because I tried it again this morning, and it went well. Stupid.

Puzzles were very nice, including this last one, and really affordable.

Thanks again, and congrats to the toppers !

So, in short, are you trying to say "I missed an easy opportunity to be on the podium"?
Congrats on your best LMI Monthly Test performance

Edited by Rohan Rao 2011-10-06 10:28 AM

Well, you never know, perhaps the top 4 players lost even more time than I did. But indeed I missed an opportunity to do a really good perf in terms of position as well as of timing (I tried again the last puzzle a few days later, and solved it quite easily). Still, 5th is not bad and since a few months I do less mistakes than I used to, so the tendancy remains positive. Thanks and congrats to you too for a good perf !