Puzzle Levels

[fblezer]

I noticed that the 'Sudoku of the Day' puzzles show a calcultated difficulty and a list of the techniques needed to solve them.

* I assume that AW Sudoku also uses some sort of calculation to determine the level of a puzzle. Would it be possible to show this number in the statistics?

* Roughly speaking, what is the correspondence between the level it gives and the techniques required?

* Will any of the puzzles it generates need Nishio or other forms of guessing to solve or can they all be solved by logic alone?

Frans

[Howard]

* I assume that AW Sudoku also uses some sort of calculation to determine the level of a puzzle. Would it be possible to show this number in the statistics?


Indeed yes! Its already a built-in function :) If you write or enter a ".", it will work out from your current position what techniques are required to complete the puzzle. If you're at the start of the game this will match the difficulty of the puzzle, of course.

It will give you its "closest" rating for the puzzle. This is usually the same rank that you requested, but because the ranks overlap somewhat, sometimes the top of one rank gets classified as the next.

The "." key also gives you the list of what techniques the solver used to reach the end, generally applying the simplest in preference. Each one is a three letter code, that should correspond to the techniques on http://www.palmsudoku.com/.



* Roughly speaking, what is the correspondence between the level it gives and the techniques required?


Very roughly, the more of the higher level techniques, the higher the ranking. Each technique contributes a "cost", which builds into the final result. Using the higher techniques more than once doesn't cost quite so much subsequently as the first time, since if you understand hidden pairs, chances are that looking for several sets won't be as hard as looking for different techniques.

I actually wrote up this technique in the Sudoku Programmers Board, and received some useful feedback which helped me tune the final values used. (I'll probably write this up again for the Palmsudoku site.)

http://www.setbb.com/phpbb/viewtopic.php?t=142&mforum=sudoku


* Will any of the puzzles it generates need Nishio or other forms of guessing to solve or can they all be solved by logic alone?


None of the puzzles generate require Nishio, but that doesn't mean you can't use it. (I often do!)

The argument that "Nishio is logic" often takes place - and I'm not enough of a formal mathemetician to argue either way, but my feeling is that it is a form of logic that is harder for most people, so I don't require it :) Later versions of the app will build in a solver that does fall back on Nishio (and indeed guessing) but because the current puzzles don't need those techniques, I didn't implement them yet.

Hope this is of interest!

Howard.

[fblezer]

Thanks Howard, I read the thread on the Soduko Programmers Board with great interest. And the "." command provides exactly the kind of information I was looking for!

As for Nishio, I'm not religious about it either but knowing that a puzzle has a straightforward solution that I can arrive at without resorting to guessing or backtracking for me adds to its elegance and motivates me to keep looking for a 'cunning plan' when I get stuck.

Frans

[scott]

In the description for the techniques used to solve the puzzle is it correct to assume that sct stands for single candidate technique? If that is so then what does dj2 or us2 stand for? Also fct?

[ab]

In the description for the techniques used to solve the puzzle is it correct to assume that sct stands for single candidate technique? If that is so then what does dj2 or us2 stand for? Also fct?

Hi,

Not sure about all of them, but in the above link to setbb.com it gives a few hints.

For instanec dj2 seems to be naked pairs and us2 to be hidden pairs.

Apologies if I misunderstood! I don't know anything about making sudoku programs myself :-)

[Howard]

In the description for the techniques used to solve the puzzle is it correct to assume that sct stands for single candidate technique? If that is so then what does dj2 or us2 stand for? Also fct?

Here's the complete list of the current tests within our Sudoku application :

sct = Single Candidate Test (naked single)
spt = Single Position Test (hidden single)
clt = Candidate Line Test
dpt = Double Pair Test
mlt = Multi-line test
dj2 = Naked Pairs. (Disjoint Subsets / 2)
dj3 = Naked Triples
dj4 = Naked Quad
us2 = Hidden Pairs. (Unique Subsets / 2)
us3 = Hidden Triples
us3 = Hidden Quad
xwg = X-Wing
sf3 = Swordfish 3
sf4 = Swordfish 4
fct = Forcing Chains Test

I often like to see at the start of a puzzle what techniques might be required. Its not quite asking for a hint ;)

[TRHeidenreich]

Ok, maybe I am just being daft, but what do you mean by ' enter a "." '? How do I enter this period? Where?

[Kristopher]

Tap once in the graffiti area.