Why a puzzle is more difficult from another ?

barbutman

Hello!

I'm a newbie sudoku player.
This does not mean that I am a bad player, because I have a lot of experience on playing puzzle games. So learn quickly ... Smile

I'm ready to create a sudoku puzzle creator program.
My big question is how to create easy or diffucult puzzles.

Of course if you reveal 25 cells on start it is more difficult than revealing 35 cells. But I'm sure that difficulty is even more than this.

Can anyone give me a good guide on this???

Thanks!

Miles · Posted: Wed Feb 08, 2006 12:36 pm Post subject:

Have you searched on this forum a little bit ?

Ruud · Site Admin

Hi,

The difficulty of a sudoku is directly related to 2 things:

1. The suite of solving techniques required to solve it.
2. The time an average player spends to solver it;

It is relatively easy to test #1. Use a solver with all the techniques built into it and solve the puzzle with it, recording which techniques were used.

Actually, for 90% of all random sudokus you do not need anything more fancy than naked and hidden singles, which seem to be the only techniques that 90% of all sudoku players know Wink

The testing of #2 is more difficult, and also more subjective. Some people have suggested to have sudokus tested by a panel of players and record the average solving time. This method is not feasable with the sheer number of sudokus in the field.

My current testing mechanism does a test of the number of placements & eliminations that can be done at any time. The more alternatives there are, the greater the chance that a player will find it. I call this the average "width" of the solving path. The second factor is the total length of the solving path. With singles only, this length will be 81 minus the number of givens, but when eliminations are required, the length of the path includes the # of elimination steps. To be thorough, each placement/elimination should be tried to find each possible solving path, but I'm not doing that, because it takes too much time.

I put a weight factor on each of the steps in the solving path (10 for a single, 30 for a naked pair, and so forth) and calculate discounts based on the number of simultaneous alternatives. This is a very complicated progress, which I'm still refining. It even discounts on consecutive occurrence of similar techniques.

You should also take a look at the #9 program by foxglove. It can show a graph of the solving path. Unfortunately I do not Mac.

Have a useful time here on the forum.

Ruud.
_________________
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barbutman · Posted: Mon Feb 13, 2006 4:54 pm Post subject:

Hello!

In fact I was at the office when I posted this message. So I didn't have much time for reading the previous posts.
I apologize for this ... Crying or Very sad

Thanks Ruud for the guide.

As I can understand the first thing to do is to create a sudoku solver.
(In fact, this is even more intersting ...)

I'm sure I'll be back, as my project grows ... Wink

Thanks guys! Great Forum !!!

Cristian2006 · Posted: Fri Mar 03, 2006 8:40 am Post subject: Difficulty

I think the difficulty of a puzzle is also related to how many steps there are, not only how many or how much advanced technics you have to use.

I think the difficulty can be described like this:
The more there are elimination steps to the solution with unforced digits AND the more those steps require advanced technics averagely during the solving, the harder the puzzle.
_________________
My new website (doesn't include sudokus, at least yet):
http://www.cristianium.fi
(it's in finnish)