You are here

Author's feedback

As an author, I like to write a few words after the tournament to explain my choices, speak a bit about the puzzles, etc..

But first : Congratulations to Kota, Rishi and Jakub for topping for this tournament. Congratulations to Tiit too, who would have taken second place if he had not forgotten to claim his bonus...
Kota's performance is impressive, he has managed to create large gaps on his pursuers. 22 players solved all sudokus, 20 without mistake.

When I offered to be an author of a GP tournament, I immediately thought I would try to create sudoku with Switzerland as a theme. Although this theme is not apparent on all puzzles, it has guided me in my choices and inspired to create the majority of grids. The code for switzerland can be SUI (International Olympic Committee code), that inspired me the consecutive sudoku, but the ISO 3166-2 code for Switzerland is CH (it comes from words « Confédération Helvétique »), thus leads me to create the arrow sudoku.
The Swiss flag is a white cross on a red background. We find that cross in the classic sudoku N°2 and sudoku palindrome, and to a lesser extent we also find small crosses in the classic sudoku N°5 and the sudoku extra-regions. Extra Regions has another motivation: we have 4 official languages ​​in Switzerland: German (65.6%), French (22.8%), Italian (8.4%) and Romansh (0.6 %). Thus I wanted a sudoku with 4 extra-regions.
As you probably know, the watch industry is important in Switzerland. I created a sudoku representing an analog watch (classic N°3, pi in the center rounded the corners) and the "clock sudoku" is the digital version. A favorite Swiss sports is skiing. In winter, the ski resorts are totally taken over by the Swiss population. It gave me the idea of ​​creating a "slalom sudoku", which is nothing other than a renban sudoku presented in another way. However the fact that there is a renban group in each line makes this sudoku unusual and for that reason, I allowed myself to name it differently. The classic sudoku N°1 can be seen as a reminiscence of the slalom. Skiing being practiced in the mountains, I could not miss the opportunity to try to represent our most famous mountain: Matterhorn (, which inspired me the thermo-sudoku (you will notice that it is quite consistent that the temperature drops more you approach the top!).
It is not easy to make the link between the “point to next sudoku” and Switzerland. This is the legend of Guillaume Tell with his crossbow that inspired me this sudoku.
And finally , although I must admit that the Swiss political decisions do not inspire me much sympathy in this time, the classic sudoku N°4, with its particular pattern of odd and even numbers (note the number 9 in the center of even numbers and the number 8 in the center of odd numbers) represents Switzerland in the middle of the European Union, which it does not belong to.

Obviously, besides the aesthetic aspect, I always kept in mind the guidelines of the organizers of the GP, and tried to create puzzles whose resolution and logical path are interesting, what is more important than aesthetics. I chose the classic sudoku N°5 as upper limit with regard to the difficulty for classic sudoku. It can be solved by identifying an X-wing of 1s in rows 2 and 8 and a skyscraper pattern of 9s in cells R3C24 and R7C26 if I remember correctly. In the coming weeks, you will find one or two more sudokus that I created for the event on my blog (, but that don't have been chosen finally (mainly due to excessive difficulty, some of you know my penchant for creating sudokus that require a good dose of patience before being solved).

I hope you had as much fun to participate in this tournament that I had in creating those sudoku.
I also would like to thank Hana, Thomas (and Wei-Hwa for the puzzle competition) and Karel, who do a considerable amount of work so that the authors have only one concern: creating the puzzles.


driv4r's picture

Hi Fred!

I only managed to solve the 4th sudoku using the 50-50 method i.e by trying one of 2 possible numbers, and I had to do it in more than 1 square to get it solved. At first I tried hard to solve it logically, which took me quite some time and I wasn't able to solve it on time.

So, was it actually possible to solve it logically and how?

Hi driv4r,

It is possible to solve this classic sudoku logically:

The important steps are: a pair 57 in box 7 (row 9), which allows you to place the 6, and then you see another pair 29 in this box, then you can place the 8 and 4. After having place all even digits in boxes 1, 2 and 3, the hardest step is to see a triple in box 8 (4 can only be placed in R8C5, R9C5 or R9C6, 8 in R8C5 R9C5, and 8 in R9C5 R9C6), this 248 triple allows you to place the 6 in column 6: R4C6. Then perhaps you'll need a few other pairs, but at this point there are no more hard step.

(There are pairs 13 in column 3, and 24 in column 7, that was one of the first ideas I had when I created this sudoku, but you really don't need them to solve it.)