Post Excavation #2

Many solvers made a comment on the Killer Sudoku – either it was unreasonably hard or it was one of the most beautiful puzzles they have ever solved. Couldn’t tell whether you did the right thing, huh?

I met up with Sinchai at the annual Thailand Puzzle Open last month and we went through the Killer Sudoku together at McDonalds. Here are some of his notes on his own puzzle:

A: If 9 is placed in the 13-cage, it will need to be grouped with 1 and 3 (to get 13). We know 1 has to be in one of the top three cells (since 1s will be in the 7-cage and the 8-cage). Therefore, the 9 has to be in R9C9.
B: 1 cannot be in the 15-cage because it will need to be grouped with either: [9 and 5] and we can’t use the 9 or [6 and 8] and we can’t use them since the 22-cage will either need [9,7,6] or [9,8,5]. Lastly, the 7 can be placed by adding the regions to get 45.


C: 1 can be placed in the 8-cage.
D: Take a look at the bottom row: the two uncaged squares and one cell in the 13-cage has to contain 6, 7 and 8 since they can’t be anywhere else in that bottom row. Note that 6 and 8 can’t both be in the 13-cage. Since we see the 23-cage needing 9, 8 and 6 – R9C3 has to be a 7.
E: 1 is forced to be in the 15-cage and has to be grouped with either [9 and 5] or [6 and 8]. If [6 and 8], we can see that the first column will have no place for both 6 and 8. Therefore the 15-cage has to be comprised of 1, 5 and 9.
F: The three blank squares of the top left 3×3 box must add up to 24, namely; 9, 8 and 7. Using simple slice and dice we can fill in those 3 cells.

killans3G: After you fill in 9, 8 and 7. Relay the information down to the 23-cage at the bottom. You can see the third column can be broken down into unique pairs; which leaves a 2 at R4C3. (H)
The 8-cage houses 1, 2 and 5 so it will share 1s and 2s with the 7-cage at the bottom. The 5 and 4 must be in the same column, therefore you can now place the 3 and 5 of the bottom left 3×3 box.
J: That leaves 3 and 4 in the 2nd column marked as shown with 6, 7 and 8 remaining in the 1st column.
K: Only possible location for the 9 at the left-middle 3×3 box.
killans5L: Still keeping track of the 9s, you can see that the three uncaged cells of the upper middle 3×3 box adds to 22, which needs a 9. The only place for the 9 in the 6th column is therefore, R4C6.
M: Careful here. The 3 has to belong in either the 13 or 15-cage. If the latter, there is no way to get 15 using [3,?,?]. There are no more big numbers available. So the 3 has to go to the 13-cage.
N: Similarly, the 5 can’t also go to the 13-cage as [3,5,?] needs another 5 to get 13. Therefore, the 5 goes to the 15-cage.
O: As we’ve pointed out earlier (at step D) that R8C4 has to be 6, 7, or 8. The 5 has to go in the 8-cage, making [1,2,5]. Now, several cells can be filled in.killans6P: 2 is forced by the 7 and 8-cage to be in the 15-cage making [2,5,8]. The 13-cage is therefore [3,4,6].
Q: 8 can be filled in R9C4 leaving [6,7,9] for the 22-cage. 3 and 4 can be placed in their uncaged cells.

We’ll leave it here for now.
Those were Sinchai’s initial steps and from here on he believes simple notations should get you through the whole puzzle. A very tough Killer Sudoku indeed.

The solutions to all the puzzles have been combined into this PDF


Post-excavation #1

All the Sudoku Excavation pages at the menu have been taken down. You can still get the puzzles here:
Large 9×9 puzzles
Small 6×6 puzzles

Solvers were asked to guess the authors of the puzzles, scoring points by doing so. Here’s a rule of thumb: if the sudoku is of a math-related variant, contains little givens and is frustratingly difficult then you can sanely bet that Sinchai wrote it. The guy loves solving and making math-variant sudokus. Or he just likes mathematics. Did you know that he scored 100% in our country’s Mathematics National Entrance Examination? Well, you do now.

You can see the rule in effect since Sinchai was responsible for the murderous Killer, Fortress and Sum 100. Others include Thermometers, XV and Consecutive. I wrote all the small puzzles (except the Consecutive), Kropki, Even Odd, Arrow and the final Mammoth fur puzzle.

Speaking of the last puzzle, Mark Goodliffe says that it’s always so much more fun when a puzzle (hunt) builds towards a finish.
I agree!

A very diligent Nick Brady: I did this in one session lasting about 7 hours and had much fun with it.
Now you know what to do on your next intercontinental plane trip.

Ivan Koswara: I just threw the Classic Sudoku to some online solver.
You cheater, you.

James McGowan: Can I assume Tamziania is somewhere near where you live?
Tamziania is a Google Map snapshot of the hospital car park where I am currently studying (and losing most of my sleep) at. As a shout-out, I also plan to use you dearest readers as characters in future events. Keep an eye out for yourself!

Zbigniew Laskowski: I thought I would become a killer myself when I received the killer clue from Fortress and realized that I had spent so much time solving that killer without the clue.
You can hunt down Sinchai for that, I’d never do such a thing to my readers. 🙂

Extra thanks to all solvers who fill in the comments box, my favourite part of an event is selecting some of them to post at the end (like the few above). So that’s my side of things. Sinchai might have a few words when his boss isn’t requiring his attention.

Results of Sudoku Excavation

One month just flew by didn’t it? 28 solvers headed out to Tamziania, dug up fossil pieces, assembled the Sudoku Mammoth and eventually conquered the mighty beast. Here is the list of solvers in the order of submission: Swaroop Guggilam, Fred Stalder, Stefan Tomlins, Zoran Tanasic, Oliver Rubio, Antonis Lalatsas, Branko Ceranic, Valerie Alexandre, Nikola Zivanovic, Valerie Garcia, Matt Stephans, Nick Brady, Franck Wallez, Prasanna Seshadri, Neil Brown, Todd Geldon, Mark Goodliffe, Eva Myers, Joshua Zucker, Sumet Juariyamark, James McGowan, Ivan Koswara, Zbigniew Laskowski, Rakesh Rai, Stefano Forcolin, Grayson Holmes, Manea Constantin and Bastien Vial-Jaime.
*[ETA: Fixed typos]
finalpuzzlesudex At the conclusion of our exhausting project, I asked solvers to guess who wrote the puzzles that form the fur of the Sudoku Mammoth. Since me and Sinchai aren’t that prolific (yet), most of the responses were probably guesses anyway. Certain points were allotted for each correct guesses and the maximum total is 50 points.
Note that all the point values in the table below are doubled (since I got lazy with decimals) but this doesn’t affect the standings.
Here are the results with the top 5 being omitted: sudexressneak Please don’t be discouraged by the standings, as they are most likely to be guesses and someone has to win. So who’s missing? 
Let’s introduce our top 5:
First to submit was Swaroop Guggilam, he was either the first or second to send in an entry throughout last three events. What an early bird! Coincidentally, second to submit was Swiss sudoku legend Fred Stalder, one of my favourite sudoku authors. This is his first entry at SOTR. He writes for many offline and online venues and all the puzzles are collected in his blog; and you can find that address in my blogroll. Two more newcomers made it to the top 5; one is Valerie Garcia; thanks to Fred who posted about it in the French forum, she and several other French names found out about our expedition. The next lucky newcomer is Stefano Forcolin who I’ve met and exchanged a few words with at the 2013 WSC. Lastly is Eva Myers, she made it to the final 8 of rock-paper-scissors way back in the first Nikoli Hurdles, good to see her back!
Now the final results…! sudexres Congratulations to Valerie Garcia from France scoring a whopping 94/100!
Interesting that Fred actually had more correct guesses at 9/10 but Valerie’s total is one point (initially 0.5 before the double) higher. More interesting is that one more competitor also scored 8/10, which is Zbigniew Laskowski who ended up at 6th place because his two incorrect guesses were worth higher points.

Again, all points were random and pre-determined which shows how it came down to luck for this little prize draw. For winning, Valerie will receive the Mammoth Book of New Sudoku by Gareth Moore. We have now come to the end of Sudoku Excavation. I will post solutions and comments about the whole event throughout the next few weeks. I would to thank co-author Sinchai and all 28 of you who’ve made this event so enjoyable.

Construction of my next event is already underway and it is scheduled for April. All I can say is it will include a variety of puzzles combined into one nice little theme. Pop back here for more details or subscribe to get notifications in case you forget!

Bye for now!

Final week for Sudoku Excavation

We are now approaching the final week of Sudoku Excavation. If you are still out there digging in Tamziania, you have a few days left to go. All submissions that I have received thus far are replied with a confirmation e-mail.

Apologies for late replies, I’m usually much more active online than this, so these confirmation emails may take up to 3-4 days.

If you’ve entered and have not heard from me, please check that your email address is spelt correctly in the submission form and try submitting again.

Tracing back the Sudoku Mammoth

Starting 2015 with SOTR’s first sudoku event:
Rumour has it that 29,500 years ago, the Sudoku Mammoth (Mammuthus sudoticus) walked the earth. Using the latest technology, scientists have made a riveting discovery! The patterns on the fur of the Sudoku Mammoth looked suspiciously familiar. The puzzle experts of SOTR were consulted and together, they have reached a conclusion. Those patterns contained symbols that are strikingly similar to what we see in today’s sudoku puzzles. Maybe we are simply creating what our ancestors have already long discovered but had been lost in the test of time.


Recently, we have narrowed our field of search to the Great Plains of Tamziania. We believe the final pieces are hidden somewhere in the map above. Join forces with our team of archaeologists to uncover more secrets hidden within the remains of the Sudoku Mammoth!

Your gear:
Here is the Instructions Booklet containing all the possible types of sudoku you will encounter along your journey.
Here is your Project Map to complete as you shovel along the Great Plains of Tamziania.

To dig one area on the map you have to solve a sudoku puzzle (small puzzle for small area, large puzzle for large area). Several areas will contain fossil pieces which give information about the Final Puzzle: the Sudoku Mammoth’s Fur in your project map.
Puzzles can be found in SMALL AREA and LARGE AREA on the menu above. Enter your answers at SUBMIT SOLUTIONS and when you’re done with the final puzzle, head to END PROJECT.

You can find more details at the “About Sudoku Excavation” tab on the menu above.

Grab your shovel and start ploughing for clues!

Let’s go dig fossils

Announcing the first event for 2015, boy do I have a lot planned for this year. Hoping most of them actually escape to see the light of day. Sudoku fans can rejoice as this event is jam-packed with a lot of tasty sudokus.

This is the first time that the event is a collaborative effort. My teammate, Sinchai Rungsangrattanakul, crafted quite a number of nice sudokus more than he knows what to do with them. In a couple of weeks, I will be sending you off to dig for fossils in…


There will be a crazy twist!

Lucky solvers might need to solve only a few puzzles to finish… whereas the not-so-lucky ones might have to solve one sudoku after another…and another.

All that coming soon!