Double Dutch Sudoku Advent (13) - Renban vs. Quad Sums
(Published on 13. December 2014, 12:00 by Richard)
Eisbär (Arvid) and I have created a fresh sudoku advent calendar in which we combine a well known variant with a relatively unknown variant every day. Combining variants leads to interesting and surprising new solving techniques.
Logically solvable
All puzzles can be solved completely logically although the logic is sometimes well hidden and is inherent to the combination of restrictions that the different types offer. For that reason we have written some solving hints for most of the puzzles, published in a very tiny font. If you want to read the hints, simply copy these in a text editor and enlarge the font size.
Renban
Place the digits from 1 to 9 in every row, column and 3x3-block. Digits in coloured areas form Renban groups. These groups contain consecutive digits, in any order.
Quad Sums
A circle at a corner implies that one digit is the sum of the remaining three digits at that corner.
Solving hints
The digits in R2C8 and R8C2 are both part of two Quad Sums. Both cannot be the highest digits of the sum. So, both are a low digit with maximum of 2. (You can determine that it can’t be 3 or higher.)
So, R2C8 and R8C2 are 1 or 2. Taking into account that the total sum in a 3x3-block is odd and the fact that the total sum of four digits around a Quad Sum dot is always even, you can figure out that both R2C8 and R8C2 have to be odd, so they are both 1.
Quad sums in block top right: {1247} and (1359}
Quad sums in block bottom left: {1269} and {1348}
6 in block bottom left in R7C3 or R9C1. :=> 9 in block in R79C2
9 in R3 not in R3C1, so must be in R3C7; R2C7 and R3C8 = pair {35}
9 in block top left locked in R1C13; 8 in R2C1 or R2C4; not in R2C3
R78C3 = pair {38}; R7C2 = 4; R9C1 = 6; R9C2 = 9; R8C1 = 2
Solution code: Row 5, followed by column 5.
Comments
on 1. April 2022, 13:05 by Nick Smirnov
F-puzzles:
https://f-puzzles.com/?id=yam5ak92
CTC App:
https://tinyurl.com/3dnmjfuf
on 18. December 2014, 18:27 by Zzzyxas
Nachdem ich das Rätsel dreimal erfolgreich in einen Widerspruch geführt habe, bin ich auf die Idee gekommen, nochmal die Regeln genau zu lesen und habe festgestellt, daß gar nicht alle Kreise eingezeichnet sein müssen.
Jetzt bin ich fünf Tage im Rückstand, hoffentlich schaffe ich es noch vor Weihnachten, das wieder aufzuholen.
on 13. December 2014, 17:44 by Alex
just over halfway through this wonderful and intricate Adventscalendar, a big 'thank you' from me too. :)
on 13. December 2014, 15:48 by CHalb
For me this is - once more in Richar's oevre - a small masterpiece with a special character in it.
on 13. December 2014, 14:38 by Rollo
Wunderschön!
on 13. December 2014, 14:23 by Richard
Fixed a minor typo in the hints. Thanks CHalb and Eisbär.
