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“COOL” for Monday
I just posted today’s puzzle – rated “cool”. Remember, this is on “easy, cool, thinker, brain, iq, insane” scale. The difficulty is shown in the image along with the numeric indication of the difficulty. So this number can be used to compare two puzzles that have same difficulty levels.
Thanx to R.Spurgeon who was quick to spot that I didn’t put the grade of the puzzle :), which was later corrected.
Later today I will post a “classic” Sudoku.
Complex innies/outies
One of our visitors (Phyllis) asked about the puzzle posted on October 13. Now, this puzzle definitely doesn’t need any trial and error to be solved – in fact it’s only rated as “thinker”. However, it requires a technique that in the new version of Perfect Sudoku will be called “complex innies/outies”. It is basically the same as regular innies/outies except that you should look for a more complex “structures” than just single nonets/rows/columns.
Here is more precisely what I’m talking about. This image shows how far you should get using standard techniques:
Click on the puzzle thumbnail to access the puzzle.
Have a look at the “structure” that is outlined in red. It consists of 3 nonets and therefore the sum of all numbers in it should be 3*45 = 135. And if you pay some attention you will see that there is an innie for this whole structure in the bottom left corner of nonet number 9. Therefore it’s value must be 135-(10+11+14+18+4+13+8+28+13+7) = 135-126 = 9.
From there a few more innies/outies spawn and then you should be able to solve this baby with standard sudoku techniques (namely – naked/hidden/match pairs).
Check the Solving tips section for more details on innies/outies.
Posted in Free sample puzzles, Solving tips
Tagged innie, INNIES, IQ, outie, OUTIES, Perfect Sudoku, solving tip, solving tips, standard sudoku, technique, THINKER
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Puzzle difficulty rating
As promised, I’ve implemented a difficulty rating system in my Perfect Sudoku software and from now on I will be publishing the level for each puzzle. I’d like to get some response from you on this – how do you rate these puzzles that I’ve been posting?
Here is what I came up with. These are the categories that each puzzle can fall into: easy, cool, thinker, brain, iq, insane. Insane is reserved for September 27 and similar puzzles :). I checked the rating of the puzzles that are currently available in the archive and I got these ratings:
October 7 = thinker
October 8 = iq
October 10 = thinker
October 11 = cool
October 12 = brain
October 13 = thinker
October 14 = thinker
October 15 = brain
This is all still being defined, so it’s not final. It is very likely that it will be changed.
What do you think? The more responses I get – the more accurate will the rating system be!
Cindy’s puzzle
Cindy, one of our regular visitors kindly asked me to post a daily puzzle today and I couldn’t say no :). So, even that I usually don’t do it on Saturday’s – you can find a very nice Killer Sudoku on the Daily page. It’s interesting that this one after the usual procedure of finding innies/outies can from there be solved either by using “cage splitting” or by using some of the advanced “classic” Sudoku techniques, such as match/hidden pairs/triplets etc.
I hope you enjoy it. As you can see, we DO value your feedback!
Posted in Killer Sudoku
Tagged Cage Splitting, innie, INNIES, IQ, killer, killer sudoku, outie, OUTIES, technique
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Samurai of the week
Samurai X for Saturday, October 15 – this is the only place you can find these kind of Sudoku puzzles!
Basically, not only do you have to fight against 5 interconnected Sudokus, but you also need to be carefull about the diagonals: ALL diagonals in the puzzle must contain one occurrence of each 1-9 digit. The diagonals are marked in the puzzle so you wouldn’t forget about them.
Click on the puzzle thumbnail to access the puzzle.
Weekend Samurai
So far I’ve posted 3 Samurai puzzles so on average it’s about one per week. I think it’s about time to make it “official” – from now on, we will be posting a Weekly Samurai puzzle on this site. These puzzles will be available through the “samurai” link on the right hand side. Please do post comments on these puzzles, if you want them harder or easier than the ones that I’m posting.
The next Samurai puzzle will be posted in a few minutes and will be available here.
1st month recap
This site was launched on September 14, so today is one month since the launch. I am happy to announce that yesterday we had 821 unique visitors to the site and more than 4000 page views. For just one month – I reckon that’s pretty good.
Most of our visitors are not surprisingly from UK and (a real surprise) from Spain. This is really interesting and I’m quite happy about that :). Will have to learn some Spanish tho, so I could communicate with my visitors properly ;).
Anyhow, we will strive to provide even better puzzles and more fun to our visitors. I posted two new puzzles a couple of hours ago and for the weekend you can expect something very special on these pages.
Thank you all and keep coming!
Non-symmetrical Killer Sudoku
Today’s Killer puzzle is not symmetrical as you would expect. So, if you find an innie in one spot, it doesn’t necessarily mean that there is another one in the opposite corner. It also has some really cool cage shapes. Otherwise it’s a little bit easier than yesterday’s. To mix it up some more, I made it diagonal. I hope you enjoy it.
September 27 solved!? Or…
I’ve received a possible solution for September 27 puzzle using only minor trial and error from udosuk. Here are his comments. You can also download the images that he sent:
Firstly, the first pic (dk0927a.png) shows the steps I last posted which narrows R[1,2]C7 to {25} and then some more… From there I’ve worked out the steps which could “nail” R1C4 to 1 like fred did, but with shorter and simpler steps. Moreover, I never branch more than 1 level, so it could be considered as “minor T&E”… here is the analysis: ——— (From the pic dk0927a.png) Firstly, if R3C4=1, then the 11-cage must be 4-2-5, and R[1,2,7]C5 must be 4-5-2 to get the 11 total. Then R[1,2]C4 will be forced to be {67}, and we can’t make up the 14-cage because R1C3 cannot be 1! If R1C5=1, then the 11-cage must be 1-8-2, forcing R2C7=5, and R[1,2,7]C5 must be 1-2-8 to get the 11 total. Now, with the top 19-cage, R[2,3]C6=19-2-5=12={39}, so R[8,9]C6={67} (9 excluded). Next we consider the 14-cage. Obviously R1C3 must be 3 or that cage will total at least 15. So, R4C3 must be 2, and the R[8,9]C3 will be forced to {4,5} (9-cage). Because R9C[3-5] is a 12-cage, now R9C5 cannot be 9 (4+9>12), so R8C5=9, and R9C5={45}. With the bottom 19-cage, R7C4+R8C[3,4]=10. This forces the 3 cells to be {145}… so R7C4=1, R8C4={45}. From here, we get naked pairs of {45} in both the row 8 and row 9. Look at the 7-cage R[8,9]C9, it can only be {2,3} now! (The pic dk0927b.png shows this situation.) Hence, R1C5=1 will lead to a contradiction. Hence the 1 in nonet-2 must be in R1C4, making the 11-cage 4-2-5. So, R2C7=2 and R[1,2,7]C5 must be 4-5-2 to get the 11 total, forcing R9C5 to be 1. Now, with the top 19-cage, R[2,3]C6=19-2-5=12={39}, so R[7-9]C6={678} (hidden triple). This makes R3C5=8 and R8C5=9, and forces R[7-9]C4 to be {345}. With the bottom 19-cage, R7C4+R8C[3,4]=10. This forces the 3 cells to be {235}… so R8C3=2, R[78]C4={35}. Now R9C4 must be 4, making R9C3=7 (12-cage)… from now on everything should fall into place pretty easily. (The pic dk0927c.png shows the current progress. I think most people can complete the grid from here…) ——— So this sort of “logically” solves your puzzle… And I think it’s impossible to be solved without using any “minor” T&E steps. Apart from the sequence which contradicts R1C5=1, all others are relatively short and simple. Thanks for your terrific puzzle… hope people will be satisfied with this “proof”… regards, udosukI can only sincerely thank to udosuk for all this work. Also, I checked the solution in Perfect Sudoku software (my development version which has a new solving algorithm) and I can tell you this: after solving 1, 4 and 5 in the top-center nonet as described by udosuk, the solver was able to find the solution without trial and error, using only “innies/outies” and cage splitting!
Progress update (on behalf of udosuk)
This is a progress update on solving the puzzle posted on September 27, sent by one of our most active visitors – udosuk. I see that “fred” has posted more details on this. If you have a file that would like me to post on this topic, please do send it to sudoku@djapedjape.com
Download udosuk’s file showing current progress.
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