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Monday, July 21, 2014

Beginners Contest on LMI

I authored the July Beginners Contest on LMI. This was a short contest consisting of 4 Classic Sudokus and 4 Sudoku Variants. The difficulty was aimed at ensuring new comers to be able to solve these. The contest was held from 23rd July - 28th July, 2014.

The Sudoku Variants that appeared are Arrow, Diagonal, Extra Region and Trio. You can view some examples here.

You can discuss about the contest on the LMI Forum.

There were totally 295 participants across 38 countries! Congrats to sworls (USA), Mehmet Eren (Turkey) and Vidhya (India) for being the top-3 Beginners. And congrats to Kota Morinishi (Japan), Timothy Doyle (France) and Hideaki Jo (Japan) for being the top-3 Seasoners.

You can view the Complete Results.

Overall from the feedback I received, most participants enjoyed the 'easy' Classics. Among the variants, Trio is always easy, Diagonal was easy, Extra Region was medium and Arrow, well, Arrow was something, right? The Arrow Sudoku was certainly challenging, especially for beginners, but I don't think it was too tough :-)
Maybe you can decide for yourself after checking the solve below:

This is the puzzle:

The 'long' arrow has to be '6'. After that, I admit, the next step is not straightforward. Intuitively, I thought people will target the bottom-left, and there is an opening there. You should get the following pencilmarks using simple addition rules and constraints.

If you look at R8C4, it cannot be '2' or '3' because it will result in the following contradictions for those two arrows. This is not very easy to identify, but filling those two arrows is quite tight.

Hence, R8C4 is a '1'. From here, the solve is smooth.

At this stage, R8C3 cannot be '3', hence it is '2' and that will also enable the other arrow to be completed. There are other ways too, but if you try filling up box 7, along with the arrows, there is just one possibility.

Using Classic rules, you can reach this stage, with those two possibilities for '5' in box-8.

The arrow in box-2 covers R1C5 and R2C6. Minimum in R1C5 is '3' and minimum in R2C6 is '6'. So, it has to be 3+6=9, which will also give you the 5-9 pair in box-8.

The centre box can then be completed, which will give you a few more digits using Classic rules.

The arrow with '7' can only be 1-6 and you get a few more digits.

You have just one arrow left to complete, and eliminating '4' is simple since neither 1+3 nor 2+2 is possible. Using '8', you should get 3+5 and the rest gets solved using simple Classic rules.

So, what do you think now? Tough? Maybe not that much!

This Arrow Sudoku was not very trivial and a lot of solvers struggled on this variant. But I hope you enjoyed solving it at the end.

And, I hope everyone enjoyed the sudokus in general, and thanks for participating in this contest! :-)

Monday, July 14, 2014

Happy Birthday Nanamma!

I created an Alphabet Sudoku for my Grandmother's birthday themed on her name. Her name is Shanta Murthy and she loves solving all kinds of puzzles. She solves most of the online puzzle contests at leisure during her spare time and usually completes solving all puzzles, sometimes taking multiple weeks for difficult ones! (I myself give up on really tough puzzles :-) )

She turned 82-yrs on 14th July, 2014 but has a puzzling mind of a 28-year-old. She feels proud of all my puzzle-related achievements but is too shy to compete herself. I keep telling her she will easily win an over-75-years category prize (if there was any!) and I still hope some day she does.

I lovingly call her 'Nanamma' (which means 'paternal grandmother' in our local language) and I dedicate this Alphabet Sudoku to her.

Nanamma solves more puzzles than me every week and it has helped keep her mind active and agile through these years. I hope she continues to enjoy solving puzzles and maybe some day she'll create one for me :-)