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!
Hi dj.. Your grading system is sure different to the Times. Your Easy is harder than the deadly ones printed in the Times.Keep the more difficult ones coming.
DJ – can you explain how you store a killer sudoku puzzle as a text file. Today’s killer for example starts out as 3×3::k:4873:1281:1281:1292: …
There are 81 quadruplets and they seem to refer to r1c1, r1c2, r1c3, …, but I would like to know how. Thanx.
I propose a monthly killer sudoku contest – but the winner is the one who solves it in the SLOWEST time 🙂 Clearly that person has had the most fun for the longest period. I typically solve these puzzles with the cat sitting on my lap. Perhaps take the dog for a walk while I ponder a tricky nonet. A glass of wine often helps getting round a particularly troublesome bottleneck. All in all a very pleasurable experience. The longer the better 🙂
fdkr, I’m not really sure why would you need that information about storing killers and I don’t know if you will understand this explanation (probably not if you’re not an IT person), but here it is:
Each number represents a combination of the cage sum and the cage id. Lower 8 bits are the cage sum (which is shown in the puzzle) and upper 8 bits are the cage id. It could be the other way around I can’t remember :). So, for each cell I store which cage it belongs to and what that cage’s sum is.
Good luck with whatever you intend to do with this! 🙂
Hi djape, Good night from Spain, one, large and free.
Thank you very much for the sunday´s killer. That insane´one takes me about one hour. I´ve enjoied it too much. Go djape, Go. I can´t spend ne day without visiting your site. Congratulations!!!!.
The sunday´s insane was great. It was difficult just woochy like. As we say in Spain, “de puta madre”. Greetings form Spain.
P.D. Excuse me. My english needs an intensive care.
Because of problems I had entering puzzles, I studied the files to see what was wrong. The upper 8 bits are the sum and the lower 8 are the id. I discovered that if you set the sum of a cage and then add another cell to the cage, it will set the cage id but not the sum on the added cell. Also, you can end up with a cage that is in two separated parts. That is difficult to fix without finding the right numbers in the saved file and change the ids.
There is also several interface features I think would help the program out: pause button, option to create diagonal puzzle, printing killers, ability to save progress, etc. I started a program for regular sudokus a while back and started adding killer sudoku features, but my solver code is still quite slow, so I use Perfect Sudoku mostly.
Djape
I’d like to order 30 copies of your killer book and have them sent to Japan in time for xmas. How can I do this?
Mike Japan
What Sunday’s killer (as gherard says)? Are you working weekend too? Let me know, please.
Greetings
Firstly, I reckon there are two types of killer players – “Space age” and “Stone age”. Space age players (like Udosuk) use their computer while Stone age players (like me) use a pen and paper. It would be interesting to have a vote to see how many of each there are.
Secondly, re Brian’s question about why the puzzles are numbered how they are, I have two theories. My first theory is that it’s a code for how long it took Djape to complete each puzzle. The first 4 digits are seconds. Divide by 60 to get minutes, then divide by the last digit and you get 32minutes and 24 minutes for the thinkers, and 5 minutes for the cool. My second theory is that it’s a randomly generated number as stated at the top of this page. Mike Japan
Lastly, in Wednesday’s Thinker, how many people spotted that if you start with the bottom right nonet, you can deduce exactly which numbers comprise each cage ie;the 22 cage must equal=679 etc.
Now, I must go and seriously get a life!
Mike Japan
For solving killer sudoku offline I have found the following table very useful as it lists all the possible combinations of cage sums: http://www.di-mgt.com.au/sudoku.html.
Mike that’s a great idea – I will make a new poll to see how people solve their puzzles. The current poll has been on for quite long anyhow.
Thanks!
Oops. The link above for the table should be:
http://www.di-mgt.com.au/src/sums.txt
And for some reason clicking on the link in 29 does not work, though it does work if you type the address in the address bar.
I have discovered a method for dealing with a block which has one innie and one outie (it also works with two innies or two outies). If you name the innie say x and the outie y you are able to set up an equation which resolves to something like x + 1 = y (for example). This allows you to eliminate all numbers in the two cells which do not fit into this equation. This sometimes leads to immediate solution of the two cells.
I have not seen this method described elsewhere but maybe I’ve not looked hard enough, or misunderstood a similar description.
Either my brain was on a go-slow today, or the puzzle was HARD. Spent an enjoyable couple of hours, with pencil and eraser, definitely wouldn’t use the computer! The whole point of doing them is to use one’s own brain – the harder the puzzle the better. Keep the harder ones coming, the easy ones (like yesterday’s) are finished too quickly. Would like a book for Christmas or else extra puzzles, please.
Using a program to work on a sudoku doesn’t make the puzzle any easier. I use the program the same way you use pencil and paper. Sure the program allows one to cheat, but that takes the fun out of it.
Just finished BRAIN (83158), my first killer! Amazing!!
Du!!, from São Paulo – Brazil
Don’t know why I started to do so, but I use MS Paint to solve the puzzles. I have a list of small and big numbers (1-9) which I copy to where I need them. Maybe this is a medium between stone-age and space-age solving, however I’m quite fast with it (I do think so, at least) 🙂
Mike, I started the Wednesdays Thinker exactly the same way you stated.
I agree 100% with Shade, that using a program to solve killer or normal sudoku puzzles is just for convenience, plus it’s easy to check your steps after you solve the whole thing, so helps a lot in writing a walkthrough. Probably a personal preference thing, like some prefer walking to the station and some drive…
So just voted among the 6 out of 54 (so far) as a “computer” solver… not as “combined” though – only writing on newspaper puzzles. However, the “pen and paper” option kind of amazes me, because it implies “no pencil marks” and apparently most users here don’t use pencil marks at all! (Alright just joking so no need for anyone to jump at me for that ^_^)
The above method can be expanded to more than two innies/outies but the resulting equation (e.g. x + y + z = a, where a is known) is less useful because there are many more combinations that could fit the equation. However in some cases it may unlock a difficult problem. If all the variables are positive then it is more useful because then you have a sum cage, even if all the cells are disjointed. So for example if you have x + y + z = 24 then you know that cells x, y and z can only be 7, 8 or 9.
Whats the latest on the book please?
For all those people interested in a race, I thought I’d do the IQ as soon and as quickly as possible, then post my time as a challenge. At the 28 minute mark when numbers were just starting to flow, I realised I had a cage which had to have two 5s in it. After 5 minutes fruitlessly searching for my error I had to give up. Sorry.
By the way Space age players don’t have to be defensive about using a computer, we trust you.
Mike Japan
Mike I hope you’re not claiming that it’s an invalid puzzle :). Please let us know if you found the error and if you eventually solved the puzzle.
Todays Killer, really is a Killer….
After about an hours pondering I have only 1 number (7 in the top left hand “nonet”)…
There are too few “clues” in this one…, there is only 2 “cages” that can have only a limited number of numbers (i.e. 24 in top left nonet can only be 789 (as there are only 3 boxes). 17 in top mid can only be 8 & 9, and that’s it!).
I guess I could try trial and error, but that spoils the point….
Usually I finish a puzzle first time, but sometimes it takes more than one try. One of your Easy puzzles once took me 5 tries to complete. I will complete it and post my final time, but it won’t be very fast. To date I have completed every puzzle you have posted. Nighty night.
Mike Japan
Okay, completed your Friday IQ in 20 mins, while somewhat distracted by the TV (wathching the Tennis Master Cup in Shanghai… man I felt for the Chilean guy who blown it at the end). (Believe it or not.) But I was in a pretty hastily mood, so didn’t appreciate the puzzle too much in the mean time and killed off the candidates in mass with subtraction combo and other tricks without any game plan. (Normally I’d look for ways to fill the cells directly and try not to eliminate too much until stuck… like trying to hit a clean winner in tennis instead of always scrambling the ball back into court.) Definitely not a good way to play the game, albeit the relatively short time achieved. I think that’s why I think racing is not good for sudoku in the first place…
Well anyway the outline for this one is to work on the lower left region using the innies in block 2 and then work upwards to sort out the left stack. Then the outies of block 4 & 7 would sort out block 5 and then allow the middle stack and the bottom band to be filled. And block 3 & 6 would be completed last. There’s probably other ways to do it. And I couldn’t remember any particularly tricky step on this one. Maybe that’s because I eliminates candidates too hastily to spot any…
> “work on the lower left region using the innies in block 2”
Block 7 not block 2! Man I wish there were some way to edit the posts here like in the sudoku forum!
The innies in block 7 aren’t that helpful (from where I’m sitting) as one of them is part of a 3 making 13 which spreads over 3 nonets!!!!
Nothing I can think of helps here….
(I’ve tried innie & outies, subtraction combo (which I’ve been using without knowing that’s what I was using – its just common sense to me) & all my other killer skills (with which I have solved ALL of the killers in the Times)…. What am I missing….
Phew – just worked out an in…
innies & outies on top two rows of nonets 7,8,9, gives something very useful!
Hello ¡¡, i resolved the IQ in 55 minutes with pen and paper, was very amusing… thanks
correction on statement i love your puzzle for nov i solve the five puzzle at once i hope you can continue in the next week paper thanks for giving us this opportunity to solve this one
I enjoyed the 50 minutes thinking with paper and pencil of this IQ. Usually I prefer Insane, are easier, to my point of view…
Is it possibile that I completed the whole puzzle but for the 6th and 9th nonets, where the couple 37 were on two different cells each?
Didi I do wrong something? Should this be the case, there could be more than one solution…
Finding today’s killer difficult. Am I right in thinking that in nonet 9 cage marked 6 has to be 5,1 or 1,5 so that cage marked 5 can be 2,3 or 3,2
carolyn, your observation is quite right. hope it wasn’t guess-work 🙂
teostress, the puzzle surely has one solution only. 3 and 7 cannot be exchanged in nonets 6 and 9 if that’s what you’re claiming.
no djape not guess work, logic! Couldn’t be anything else. ok so far so good, still struggling though. Using innies in block 7 and logic i get the cage marked 15 to be 6,9 or 9,6 and the cage marked 13 as 1,4,8. Do you others agree?
carolyn – keep going you’re on the right track. use the information that you just said and combine it with the information you can extract from nonet 1, cage 24.
yipee done it – thanks
Finished the IQ second try in 62 minutes. (Total time 62 + 28 = 90 minutes). Had more problems tha usual.
Mike Japan
I now agree with Udosuk that a race would be pointless. If he can finish an IQ in 20 minutes (14.815 seconds per number) while watching a tennis match and without cheating, then I take my hat off to him. He’s in a different league to me.
Mike Japan
I took about an hour and fifteen minutes and started just like Carolyn. The 5 and 6 in the bottom row being my starting point, with the 4/1 option for 5 cancelling both of the options for the 6.
Very enjoyable puzzle, DJ!
Here’s how I started on today’s IQ problem — a slight trick in this one made things way easier, and while I’m sure it’s got a name, I don’t know what it is.
First off, R3C1 was pretty easy to get, but that’s the only “obvious” given I found. This isn’t relevant to the rest of this post, tho…
So there’s a 7/3 originating in nonet 3, with a 6/2 next to it. The rest of nonet 3 add to 39, so R3C78 add to 6. (51) or (42).
Consider 51: No 5 can be in the 7/3, so the 6 in nonet 3 would have to be 51. So we could have R3C7 = 1, R3C8 = 5, and R4C8 = 1. But then there’s nowhere for the 1 to go in nonet 9 (since 19/3 cannot include a 1). So we know R3C78 = 42 or 24.
So here’s the trick: we know there’s a 1 in the 7/3 from nonet 3. If the 1 were in R4C6, then we’d have what I like to call a tautology; R34C7 and R34C8 both add to 6 and both are made of a 2 and a 4. There is no way to distinguish between either order — R34C7 could have 2 above 4 or 4 above 2 (with R34C8 being just the opposite) and nothing would change anywhere else in the puzzle. So we know there’s no 1 in R4C6, which puts the 1 in R4C7.
This immediately gives us R9C78, which then gives us R1C89, which then gives us R12C1…and we’re off to the races.
Is there a name for that trick mentioned above? I mentally think of it as a “tautology”, so I can eliminate some candidates in order to limit the number of solutions to one. Maybe the “Multiple Solutions” method?
Thought friday puzzle was quite difficult but thtats the way i like them.Could somebody please explain how using a computer to solve a puzzle gives them any sense of achievement11
zd – your “tautology” is what is referred to elsewhere (eg http://www.sudoku.com forums) as “uniqueness”.
I just loved the IQ one – very satisfying. BTW, does anyone else find the Times online ones more difficult than yours – not because of the puzzle itself, but the font used makes it incredibly difficult (for me at least) to distinguish between 5s and 6s. Anyone fancy putting today’s (friday’s ‘deadly’) into your package? I’ve had to stop/reprint/start it three times because I thought a ’25’ was ’26’!
K
Sorry Richard, I can’t.
Mike Japan
Hmmm, I’ve now started getting paranoid. I don’t think Friday’s deadly adds up! These are the nonet totals I get:
51,52,57
54,43,55
35,32,25
Which to me adds up to 404 when it should be 405! Anyone fancy double checking my numbers please? Here’s the link to the puzzle:
http://www.timesonline.co.uk/article/0,,18209-1876402,00.html
K
box 3 should be 58 (presumably you read the 26 as a 25 ?)
Kenny,
THANKS for the link for Times online killer puzzles. I’ve been unable to find their killer puzzles in their “Times Online” site. I sent them an email and they said their killers appear only in the print Times.
have a great weekend. Bob
Thanks ajft,
I think I’m rolling now!
Pleasure, Bob.
K
Has anyone tried the Telegraph’s Kakuro? They are the real killers, even the so called “Gentle”. I’ve only completed 2 of the Moderates. I eventually manage the on-line Killers and the ones in the Times are getting harder.
I e-mailed the Times several weeks ago complaining about the font size but nothing happened.