Hope this is a worthwhile little bump...
I have a rather menial job of running the copy center at my high school so when all my copy machines are printing I needed something to do...girlfriend encouraged me to try sudoku. (she's obsessed!)
Quickly got the hang of it and got bored of "
easy"
books, so I bought harder and harder books. Much to my dismay, even "
hard"
books didn't use many more advanced techniques at all. Found Frank Longo's "
Absolutely Nasty Sudoku"
series and finally FINALLY found some puzzles that completely stumped me. Searched for a step-solver online, but I couldn't get to any since my school's network blocks anything relating to fun (sudoku) on the internet. Searched for solvers on my phone, and after a ton of searching (there are way too many brute force solvers...) I found a neat little app.
The app called Sudoku 10000 (get this if you have an android phone, please!) contains 8 levels of sudoku and a hint engine/step-solver/technique analysis. So I typed my stuck sudoku into the game and suddenly learned a new technique. Started making more progress on my book and every time I was completely stumped I typed it in the app and BAM learned something new. Eventually conquered my books and have worked my way up to the top difficulty on the app.
Looks like it's already been discussed earlier but according to this app this puzzle is impossible to solve (with known strategies). It took >
1 minute for the computer to move to the second step. (putting a 1 in R3C8 asserts that R9C2 can and cannot be 2 at the same time, therefore it cannot be a 2, if anyone cares. Then two more similar chains, then it got stumped.)
I guess the point I'm trying to make is yes there is still logic involved, but "
computer"
logic and "
human"
logic are very different. That particular logical path would essentially be a "
guess"
to a human even though to the computer it's nothing more than a complicated chain. The "
Nightmare"
puzzles in this app occasionally utilize far far simpler chains, but as a human I would consider these forcing-chain/forcing-net strategies to be "
guessing"
as well. Unlike all of the other strategies I know, there is no particular pattern to look for in this case, it just boils down to "
try a number, look for contradictions."
Seems like these puzzles aren't for humans to logically solve, but for humans to program a computer to logically solve, a much different feat. If I only came across these types of puzzles I would probably get bored of sudoku real quick.
As much as I love this app it doesn't beat the pencil-and-paper experience. Does anyone know if there are any sudoku books that exist that are comparable to/harder than that Frank Longo series?
.
Even more awesome is the fact that the whole paper is actually entirely understandable. 