Regional Chess Sums: A Proper Introduction
(Published on 24. January 2022, 09:30 by Nordy)
After an overly challenging first puzzle and a failed second attempt, the proper introduction to Regional Chess Sums is finally here. Many thanks to those who solved and left feedback on the first puzzle, and a sincere apology to anyone who worked through the broken puzzle before I took it down.
Rules:
Chaos Construction: place the digits 1 to 9 in every row, column, and irregular region. Each region is a set of 9 orthogonally connected cells that must be determined while solving.
Regional Chess Sums:
- Kings: digits in cells with squares are the sum of all digits that share its region and are a king’s move away.
- Knights: digits in cells with circles are the sum of all digits that share its region and are a knight’s move away.
- Rooks: numbers outside the grid show the sum of the digits up to the next region border of that row or column.
- All squares and circles may or may not be given.
Below is an example region. The 7 sees the 3+4 by king’s move. The 8 sees the 6+2 by knight’s move. The 21 outside the grid sees 5+1+9+6, which are the digits up to the next region border.
You can solve online:
For CTC and F-Puzzles, disable conflict checking to avoid a grid full of red digits.
Solution code: Row 9 then Column 9
Comments
on 25. January 2022, 21:15 by SirWoezel
Beautiful puzzle. A pretty challenging start, followed by a very tough middle part and -as a reward- an easy ending.
on 25. January 2022, 19:46 by Melriken
Well I got my grid fully colored and was quite pleased with myself and then went in and started pencil marking numbers... only to find out that I had the king in R8C5 only having one adjacent cell that it shares a region with, which can't be right obviously, but everything else is working... and now I don't know where my mistake was and it seems to have been far enough back to not be an easy fix :(
May need to start over (which will let me switch to CTC...) or go crazy...
I used Penpa+ due to the 'For CTC and F-Puzzles, disable conflict checking' comment, and regret it, I am used to CTC and find it far easier to better for this.
--Sorry to hear that! The King in R8C5 is quite potent during the middle part of the solve. I have added a few more images to the document to hopefully make your remaining solve less tedious, should you choose to look at it. Would be happy to answer any further questions as well.
++if it was easy it wouldn't be as fun... I had looked at the guide earlier (and was already past it at that point), I looked again and I am already past the new images in CTC (and much happier being in CTC)
on 25. January 2022, 19:37 by Nordy
As mentioned by comments below, this puzzle is quite a difficult introduction. Most notably, however, it is more approachable than the previous puzzle in the series, although it can be difficult to ask the right questions. There is very rough break-in guide in the comments that is not at all comprehensive, but may be helpful.
This puzzle should probably be named: "Regional Chess Sums 2: Slightly Easier and Smoother than its Predecessor but Still-Not-Quite-A-Great-Introduction"
on 25. January 2022, 12:40 by marcmees
quite hard for an "introduction" ... but worth every minute spent on it. thanks.
on 25. January 2022, 12:17 by henrypijames
https://tinyurl.com/mtdtwejt
I found this opening constellation, which isn't working out. But I don't see any way to disprove it without bifurcating this far and quite a bit further. I remember that the equivalent constellation in the withdrawn puzzle was ruled out quite quickly by counting the region in the bottom right corner, but that doesn't work here.
--You are right that you can't rule that region out quite yet, but you can give Column 1 more attention to make logical progress. Here's a very rough guide that I whipped up so I could respond quickly: https://tinyurl.com/2p9xu9u7 There is a hint at the top and then it leaves quite a bit of work to the reader. Typing it up has made me realize this puzzle is still quite hard... strategically, coloring regions seems more useful than only drawing borders, and I should have included a recommendation to use CTC because of multiple colors.
on 25. January 2022, 09:23 by polar
Agree with Jesper's comment. An improvement and much smoother solve compared to the first one, but still quite challenging in places!
on 25. January 2022, 08:58 by Jesper
It is a very nice puzzle. Easier than the first one, however still very hard for an "Introduction".
on 24. January 2022, 19:47 by henrypijames
Hope I remember the things I've learned spending somewhere between 4 and 6 hours on the puzzle that was withdrawn. ;)
—ahhh I am so sorry! The previous version “broke” 3/4 of the way through, so the lessons you learned are definitely applicable…and there is a confirmed solve already on this one, so I’m exceedingly confident it is not broken!
<<<
I actually came further than 3/4 before it broke - but of course one might argue that a broken puzzle is always broken right from the start.
On confirmed solve, I remember Phistomefel's CC Minesweeper having several confirmed solves before it was pointed out that there was an alternative option that he and all those who had solved it hadn't considered. He had to add a given digit to fix the puzzle. I, at that point, had already spent hours trying to disprove the alternative option ...
—very interesting about the minesweeper puzzle. From skimming the comments it looks like there were multiple solutions, whereas the previous chess sums puzzle had no solutions. Although perhaps I was too hasty in removing it. If you used CTC and still have your progress saved, here’s the link in case you want to finish it out with my amendment: https://tinyurl.com/2aa2w65e the puzzle is solvable if the knight in R8C5 is the sum of two cells that it sees, not all cells. (And you can see why overlooking this during testing is quite embarrassing)
on 24. January 2022, 16:36 by Siebuhh
Again a beautiful puzzle! This puzzle is easier than the previous one but still very challenging
