There were quite a few comments from our visitors, especially on the Daily Killer Sudoku page, which makes that and other pages load slow. Therefore, I have moved some of the old comments to this new category.
If you’d like to read what other people had to say about our puzzles you may find the old comment by clicking on the “comments” link below or here.
UPDATE (some 5 years later): I reopened the comments on all pages. Feel free to add your comments there, it means a lot to me!
Udosuk,
Is it 101110 ?
Mike,
The series is 0, 1!, 2!!, 3!!!, 4!!!!,…
0 = 0
1! = 1
2!! = (2!)! = (2*1)! = 2! = 2*1 = 2
3!!! = ((3!)!)! = ((3*2*1)!)! =(6!)! = (6*5*4*3*2*1)! = 720!
Help me out here Gaynor. I usually wizz thru these but I’ve been struggling on 97589 all day and still can’t get started. Just a hint how to start Please !
Ian, Shai has posted his way of solving Monday’s Brain 97589.
I have a suggestion for this puzzle that I think is easier than Shai’s:
1. R4C3=1, R6C7=6. (outies of first 2 and last 2 columns)
2. Nonet 9, number 6 can be only in either R7C8 or R7C9 (2 cell cages with sum 12 can’t have a 6). Therefore, you eliminate 6 from the rest of row 7.
3. R6C4+R7C4=7, but R7C4 can’t be 6, hence R6C4 can’t be 1.
4. You have a hidden single in nonet 5! (and this is not 5 factorial 🙂 ). R6C6=1 (you can’t have a 1 in 3-cell cage with sum 19, nor in 3-cell cage with sum 22).
From here it should be straight forward. I hope. 🙂
thanks djape got it.
What exactly does it mean if a puzzle is not a diagonal one?
1. EACH diagonal MUST contain at least one repeat
2. AT LEAST one diagonal MUST contain at least one repeat
3. AT LEAST one diagonal MIGHT contain a repeat, but it doesn’t have to (in other words, just because it’s not marked diagonal doesn’t mean it’s not diagonal)
Thanks Shai, your tip
“3. 45 rule on 4 bottoms rows revels r5c1+r5c3+r5c8 to be 8, that is {1,2,5} or {1,3,4}. both options contain a 1.”
made me solve the Monday’s brain after I got stuck directly at the beginning! Didn’t think of applying the 45 rule to four rows instead of three 😉
I’m stuck with today’s (23054) too having solved half of the puzzle… need mor time, as it seems 😉
Anne, Austria
Re Udosuk’s puzzle, I’m changing my guess coz the way his brain works the answer is probably 5367.87e!
Random,
Diagonal puzzles must contain all number 1-9 on all diagonals (no matter how many diagonals there are in any specific puzzle).
Non-diagonal puzzles can contain any arrangement of numbers on its diagonals. This, of course, includes a possibility that a “non-diagonal” puzzle (meaning: a puzzle that I didn’t mark as diagonal) could have all numbers 1-9 on its diagonals.
Think about it this way: when you solve a regular Sudoku puzzle, do you care about the diagonals once you solved it? Of course not. They are irrelevant for that puzzle.
But for diagonal puzzles, the diagonals are very important in the solving process.
Explanation of 0,1,2,720!,… answers.
1st entry is 0 followed by 0 factorial symbol.
2nd entry is 1 followed by 1 factorial symbol.
3rd entry is 2 followed by 2 “!”, i.e. 2!!=2!=2
4th entry is 3 followed by 3 “!”, 3!!!=6!!=720!
So the 5th entry is 4 followed by 4 “!”, 4!!!!.
4!!!!=24!!!=620448401733239439360000!!
(Got that from the little windows calculator application…)
For my question, the next entry is a 5-digit number, and it contains digits other than 0,1,2.
Hint: think about the relations between adjacent entries…
Udosuk,
Is it 88110 ?
Thanks, djape. I was just trying to figure out if the fact that a puzzle was not marked as a diagonal puzzle could be a useful clue.
In other words, if you had a non-diagonal puzzle with a cell that only had two candidates left, and one of them made the diagonal have 1-9 w/o repeats, if a non-diagonal puzzle HAD to have repeats, that would tell you something.
Since it could coincidentally not have any repeats, it’s not really a useful clue.
Just looking for all of the angles! Thanks again for your response.
Shai, Udosuk – I get 88110 also. But am not totally convinced.
In the rules it says that no numbers can be duplicated in a cage. Is a cage the set of numbers that the dotted line is around. I know I did a killer where there were duplicated numbers in a cage. Ex. If a cage is a L shape and the L spans two different 9×9 blocks can’t there be duplicating numbers?
Thanks
Tom, some puzzle authors allow duplication of numbers in the case you just described. However, most people agree that it shouldn’t be allowed.
Either way, I clearly stated up the top – numbers cannot be duplicated even if other sudoku rules would allow that.
Bob, DJ replied to your request before I went on-line again, glad you got sorted. I’m still struggling with NDorward’s 7th, even with the help he gave – I’m wondering why both numbers in Cage B have to be 1 to 5. Think it’s a bit obscure for me, I did all his others OK, but this one . . . .
Yesterday’s killer (COOL 23054) was too easy so I’m going back on-line to see if there are any other types to download (that I haven’t already done).
What’s the weather like in Sydney, Adele, pouring with rain here – and all that snow in China and Japan. The weather has gone mad. Hope we get a good killer today as don’t want to go out!
Sorry, meant Ian not Bob – a senior moment
Hello ¡¡ you said for today, cool killer, but when i download it, is IQ, anything wrong? best regards
I also had troubles with yesterday’s killer (23054) and found a method to solve them. I don’t know, if it is a new way, but I will post it. Perhaps somebody will find it useful.
I got stuck halfway through the puzzle, where I had a lot of fields filled with 2, 3 or 4 possible numbers but could not find the right ones.
I had a look at the 9×9-squares, where two “outlapping” sum fields made it impossible to work with the “one square must always sum up to 45” – rule. I combined the possible numbers in these fields, so that the sum was the number missing to 45 (from the square).
In yesterday’s puzzle 23054 it was the the upper middle square and the lower middle square which worked this way out.
After eliminating the not matching combinations one of the fields had only one number left, so I could go on and solved the puzzle very quickly afterwards.
Did I think too complicated and there is an easier way to go?
greez
KArin
Hi to all!
This has got to be my favorite site on the web.
I have a different kind of math puzzle that I’m trying to publish. I was wondering if anyone would be interested in trying it out and giving a constructive critique. It may appeal to you folks.
If interested please e-mail me: munromurg@yahoo.com
DJ keep up the great work – I’m totally addicted.
Thanks
Matt,
Why don’t you post your puzzle here, or if it is an image, e-mail it to me and (if appropriate) I will post it on this site. The bigger the audience the more constructive critique will be.
DJ.
Can you PLEASE provide the solution for the Dec 16 samurai sudoku puzzle in the Washington Post Express? I have worked it for a few weeks and missed the solution due to the holidays.
I am really impressed with your puzzles. I like Killer Sudoku because it offers so many different ways to solve the problem, some more elegant than others. Your puzzles are more complex than others and, therefore, create a bigger challenge. I would love to be able to generate my own. Perhaps you should consider offering your puzzle creater program for sale?
Gaynor, after some hot sticky days we finally have a medium one, thank goodness. A little rain to revive the plants, and me.
If you are looking for more puzzles have you done all at NDs site? Pat reckons they are a real challenge.
Everyone, I finally succumbed and tried a junior normal sudoku – Pats been trying to get me into them for ages. Took me 2 hours but I am now appreciating the efforts you guys put into these.
Adele
Australia
8.40am Thurs
How do I get to ND’s site?
Don – ND’s killer sudoku puzzles are posted at:
http://www.ndorward.com/blog/?page_id=71
Am I alone in finding the last IQ puzzle (152808) very difficult? It’s taken me ages to get started and I’m still not sure that I’m on the right track.
Thank You Frank.
I did ND1, but had to resort to the Trial & Error Method to complete it. Have just downloaded ND7. This one looks almost impossible.
Can you send me the solution to the Washington Post Samurai Sudoku that appeared in the January 1, 2006 edition?
Thanks.
Don–I would suggest doing them in order, as they get progressively harder! The ones from #4 through #7 (esp. #7) are enough to give even hardened solvers pause. If you’re stumped then try going through the walkthroughs that I’ve posted to get people started on puzzles #4, #6 and #7 (Udosuk has also posted a complete walkthrough for the latter). I have also listed the initial steps for #2 on my “tips” page on the site (near the bottom, to illustrate one technique).
fripper, the solution can be found in the archive:
http://www.djapedjape.com/gallery.php
I will keep all Washington Post solutions (not the puzzles) there.
Re David above, IQ 152808
I too found this very slow to get started but once I had a couple of numbers it went easily.
Suggest: split all cages you can – there are many in this puzzle – it won’t give you numbers but will enable you to see what combinations are possible – then numbers will follow. e.g. the 22 cage (2nd nonet) can be split to 10 and 12, the 23 cage (nonet4 and 7 can become 15 and 8. etc Good luck
David,
Here are some hints on how to solve the last IQ puzzle (152808):
1. 45 rule on nonet 7 (bottom left) reveals r1c7+r1c8=8. Because of the 4 cage ({1,3}), in the same nonet, this 8 must be {2,6}, and therfore r1c5+r1c6=15 cannot be {6,9} and has to be {7,8}.
2. The 14 cage in nonet 4 (middle left) is {9,4,1}, {9,3,2) or {6,5,3) (all options without 7 or 8)
3. 45 rule on row 6 reveals r1c6+r2c6=10. Since according to step 1, r1c6 is 7 or 8, this 10 is {7,3} or {8,2}, and therefore the 7 cage is {2,5} or {3,4}. However it cannot be {3,4} since this would conradict all the options for the 14 cage from step 2. So r2c5=5, r2c6=2, r1c6=8, r1c5=7, 14-cage={9,4,1), r5c3=6 (can’t have a 6 in a 12-cage of 2 cells), and r6c3/c4 is 3/9.
4. Now we do the same on the other side (remember, DJ’s killers are symmetrical…), 45 rule on row 4 reveals r4c8+r4c9=7, this 7 has to be {2,5}, because of the 14 cage in nonet 4 is {9,4,1}.
5. 45 rule on nonet 3 (upper right) reveals r4c9+r5c9 = 5, so r4c9 cannot be 5, and has to be 2 (according to step 4), and r4c8=5, r5c8=9, r5c9=3….
and you carry on….
Oops, 8) is 8 )….
My answer to the logic series is [b]41110[/b]!
I’ll let the interested to work out the logic for a few more days, if nobody work it out by then I’ll reveal it… But I’m very interested in how some worked it out as 88110?
Been very busy and haven’t got online for 3+ days, so a whole lot of djape’s daily killers to catch up!
Dear djape, I requested a couple solutions to past overlap puzzle on the “daily sudoku” page… Just wondering is it still possible to post them up? If not I’ll give up the hope…
greetings fellow killer fans. I am curious — I haven’t been getting a killer puzzle a day from this site. Is everybody else getting a new killer puzzle?
Re Matt’s puzzle (Response 77)
It looks good and after 1 hour I hadn’t finished it but had got a few answers. If you are a killer-holic and you want something to do on a killer-less Sunday, give it a try. I rate it equal to a Samurai (not a kiler Samurai)
Mike Japan
hey djape, I think its been a while since we had a Killer X, and I love them … feel like giving us a little weekend X present?
Hi everyone.
I’d like to suggest some killer sudoku lingo, so we could write faster and still understand each other.
So here it goes:
Killer Sudoku Lingo
===================
Cell combinations:
rxcy or RxCy, while x,y are numbers in the range {1..9}, means the cell in row x, column y. Counting goes from left to right, and from top to bottom.
r1c1=1 (or “r1c1 is 1”) means there’s a 1 in r1c1.
r1c1/2 means combining the cells of r1c1 and r1c2.
r1/2c1 means r1c1 & r2c1.
r1c1/2/3 means r1c1, r1c2 & r1c3.
r1c1/2/4 means r1c1, r1c2 & r1c4.
r1c1/2=7 means r1c1+r1c2=7.
Nonet – a 3 X 3 square, in which all digits have to appear. There are 9 nonets in each sudoku, and they are numbered, for the sake of conversation:
1 2 3
4 5 6
7 8 9
So “nonet 1” is the top-left nonet, etc.
x-cage – A cage whose sum is x.
Ex: “The 16-cage in nonet 2 is {9,7}”.
x/y or x/y-cage – An x-cage of y cells.
Ex: 16/3 means a 16-cage of 3 cells, 20/5-cage means a cage of 5 cells whose sum is 20, etc.
Also: x(y)-cage is the same. Ex: “11(2)-cage” is the same as “11/2-cage”.
{A1,A2,..,An} – The set of numbers A1,..,An. Order is unknown or irrelevant.
Ex: “r1c1/2={2,4}” means that either r1c1=2 & r1c2=4 or that r1c1=4 & r1c2=2.
[A1,A2,..,An] – The ordered set of numbers A1,..,An. The order goes from left to right, or from top to bottom.
Ex: “r1c1/2=[2,4]” means that r1c1=2 & r1c2=4.
Ex: “r4/5c7=[4,5]” means that r4c7=4 & r5c7=5.
Improvement: If there’s a cage who’s not in the shape of 1 X n or n X 1, The order goes first from left to right and only then from top to bottom. Ex: A 23/4-cage in cells r1c1, r1c2, r2c1 & r2c2. Saying that “The 23/4-cage in nonet 1 is [8,7,6,2]” means r1c1=8, r1c2=7, r2c1=6, r2c2=2.
=============================================
Please feel free to comment/add/suggest/improve.
DJ,
1. What do you think about it ?
2. Do you think some of my suggestions might interfere with the HTML syntax (as happens when i do “8” and “)” ) ?
3. If you think this is important you can put it in a new page, with a link from the daily-killer page, for newbies. In this case, feel free to correct my English if needed.
ND,
I’d appreciate your comments as well.
Shai, Israel
Thanks very much for telling me where I can find solutions to Samurai puzzles appearing in the Washington Post. I have written a program to solve individual Sudoku puzzles but ran into trouble with the Jan 1 Post Samurai because the solutions I came up with for the four corner puzzles created problems for the fifth puzzle (the one in the center). It was at this point that it struck me … solutions are not necessarily unique! I cannot imagine writing a program to find ALL solutions … but maybe I better try! I would be interested to see a discussion about the non-uniqueness of Sudoku solutions.
Shai & Hasher,
Many thanks for taking the trouble to reply to my recent post re IQ 152058.I eventually managed to solve the puzzle but I found it rather a slog. Clearly I need to practise more!
Thanks again.
David
Love your website- great puzzles! I can’t get enough of the killer samurai and I love the diagonal rule.
Could you please organize the site so we could find the solutions more easily?
It would be greatly appreciated.
Keep up the great work!
Shai–terminology seems fine to me: I usually use 23(3) rather than 23/3 as it seems clearer to me (I used to use square brackets but the round ones seem less fussy).
Probably the other thing you need is an efficient & clear shorthand to indicate exactly how you’re using the 45 rule at certain steps.
One shorthand I’d contemplated: when you wish to indicate in a set which numbers cannot be omitted, use asterisks: e.g. r1/2/3c2 = {6,7,*8,*9} would mean “either {6,8,9} or {7,8,9}”. There are sometimes more complex internal relationships which would require boolean operators to mark, but I don’t feel that would be useful; whereas the idea of “necessary inclusion” is a hinge of many puzzles.
Hi DJ Ape and other readers!
I am a big fan of this site and since Mid October I have not missed a Sudoku Killer here.
My question is: am I correct when only the last 5 sudokus are in the archive? And does this mean that it is not possible to find an older Sudoku from lets say October? I have been searching a lot on this site but cant find older killers.
Thanks for a quick answer!
Ron
I almost forgot…
I heard about a Sudoku Killer book that DJ Ape would have written. Is that true?
How do I order it?
Ron
Hi,
Here is another killer sudoku I designed. I called it “the frame” for obvious reasons 😉
http://jcbonsai.free.fr/sudoku/TheFrame.png
The data file for perfect sudoku :
http://jcbonsai.free.fr/sudoku/TheFrame.txt
Have fun 🙂
Nate wrote:
> Probably the other thing you need is an efficient & clear shorthand to indicate exactly how you’re using the 45 rule at certain steps.
I also thought about it but couldn’t think of anything. Reading your comment, though, gave me a spark of inspiration…
So how about:
45-rule:
“45” on R/N/Cx -> conclusion
Ex: “45” on N1 -> r3c3=1, means that appying the 45-rule on nonet 1 reveals that r3c3=1.
Ex: “45” on C4 -> r4/5/8c4=8, means that applying the 45-rule on Column 4 reveals that r4c4+r5c4+r8c4=8.
Ex: “45” on R6-9 -> r5c1=9, means that applying the 45-rule on the 4 bottom rows reveals that r5c1 is 9.
Ex: “45” on N124 -> r5c3=4, means that appying the 45-rule on nonets 1,2 & 4 reveals that r5c3 is 4.
Shai
Sounds good to me!
I was away for 2 days, so I have some catching up to do…
Ron: you are right – we only keep 5 Killer and 5 Sudoku puzzles in the archive.
The book: the PDF (online) version has been put on hold and may not even be released for various reasons. But there will be other books :). Can’t reveal too much at the moment :).
Cheers!
DJ – If the pdf version of the book is not going to appear, can you repeat the instructions for obtaining a copy of the printed version please.
fripper, you can’t solve Samurai puzzles by splitting them into 5 separate puzzle and then solving them individually. I think puzzles that can be solved that way are too boring and not “real” Samurai.
The whole point of Samurai is to work on all 5 sub-puzzles simultaneously – they all interact and give clues to one another.
Most importantly: all Samurai puzzles posted here and in The Washington Post and Express have ONE SOLUTION ONLY. If you claim otherwise – please triple check everything and then post at least two different solutions.