Feedback and Questions

hi Andrew,
It's about exocet J4.

the solver fails to eliminate, in cell A9, the 4 base digits 2.5.8.9, who can see the base cells, but it well eliminates the 2 others cell who can see the base cells (C9 and E8)

regards and thanks for your helpfull solver

Thanks Andrew, great website!
I understand you create Sudoku's as well. I assume you take a completed grid and then remove numbers/reduce but still making sure it's solvable. How do you do that? Is it trial-and-error, or is there a theorem that tells you whether a sudoku is valid? And for a Killer Sudoku: how do you determine the subdivision that still leads to a valid solution?
I've been wondering about that!
Maybe you can enlighten me.... or is that a trade secret ;-)
Regards,
Adriaan

Hi Andrew! Thakns a lot for the best Sudoku I've ever seen. There is a bug after the last update. Single notes (with leading zero) are converted to usual numbers after each page refresh. So I have to make printscreens to complete the puzzles. Please fix it.

Completed the 9/24 Zigsaw puzzle # 5339 correctly. All numbers are filled in but program did not confirm the win (green confirmation) nor display as a loss.

Very strange...

I ran into a puzzle that I solved using what I call "double Medusa". I don't use colors, it confuses me, I use letters. A/B instead of colors. When A/B does not solve the puzzle, I go to C/D, E/F if necessary. Today I found a puzzle that I solved when A/B and C/D occupied the same cell in two different places indicating that D could not be correct because it occupied cells containing and A and another with a B. All D's are eliminated. Manual testing confirmed.

Is this new? Did I do good?

A strange constant: The Daily Sudokus on Wednesday and Thursday are rated as tough - and I can't solve the Wednesday puzzle and have no problem with the Thursday issue.

Any explanation ... ?

Wow!! I input an Expert grade puzzle and tool pointed to the critical clue, the way a guide does.

Hi Andrew,

If you please could check why the grader is giving this soduku a 41 ("Gentle/Easy'). I was cracking my head trying to figure why I was taking so much time on a easy sudoku, but I found the solution uses a Y-wing, so it makes sense now.

Love the solver, it helps a lot.

Thank you

Hi Andrew:
Many thanks regarding you site. The sudoku methods are really outstanding.
This comment is regarding the killer sudoku solver which I applied to a hard problem that I got off the net.
The original problem:

https://www.sudokuwiki.org/killersudoku.htm?bd=122212221113313341221221441331121112334444422311121122122122133123313311144412221,121100000814000019000008000013001400160018150024000000180000000000000016000033000000000000001900001718000000180800000000001200000017000703001800001600000013000000

I stepped throught the solver until it ran out of known strategies.
When the solver got stuck we had candidates:
C4:1234568, E3:3456789, E4:3456789
G1:23456789, G2:1234, G3:1234

It is possible to make progress in this position:
Firstly, the points C4, E3, E4 total 19 as the total of all cages that intersect the rightmost five columns exceeds 45*9 by 19. This means that E3~3 since otherwise C4 and E4 would total 16 and have to be 7 and 9. This is impossible since C4 cannot be 7 or 9.

Also, the total of G1,G2,G3 must be 10 since the total of all cages that intersect the bottom two rows is 100. Since G2,G3 are both 1,2,3,4 G1 must be 5,6 or 7.

I'm sure that once the solver handles this type of situation it will noticably improved.

Dear Andrew,
I'm a huge fan of yours. Thanks for this fascinating website. I would appreciate it if you could clarify two things for me:

1- How the grading system works? Take a look at these three sudokus please:

920000030706000000000280605000038006000921000500740000803072000000000903060000012

701040906000000050609005000000100309080090020907006000000400703070000000403080105

009700050007050000100306970000500030200070009090004000081407006000020400030001700

First one is dubbed Extreme (score: 546), second one is considered Very Hard (score: 592), and third one is again Extreme (score: 687). How is that possible? Generally speaking, which one should I consider the most reliable? The score, or the Extreme/Very Hard/etc. descriptions?

2- This puzzle (010700400200050070000900050009008002003090600700400300070000000060010900008006030) has been dubbed Extreme Grade, Overall Score: 1199, with 57 steps to solve. However, if you remove 3 from F7, it'll still be standard, Extreme puzzle, but the overall score will reduce to 645, with 42 steps to solve. How is that possible? How come removing a clue makes the puzzle easier?

Thanks for your time! Really appreciate it.