## are solvers not cheating?

Programs which generate, solve, and analyze Sudoku puzzles

### are solvers not cheating?

when you have worked it out right you will know it is correct so what use do you have for a solver.

Most books have answers anyway.

Is it just to check that the puzzle can actually be done.
kat

Posts: 10
Joined: 19 July 2005

As I understand it the challenge of writing a solver is equal to that of solving by hand. Some people prefer this challenge to that of actually solving the puzzle in the conventional way - but you have to know the best way of solving any of the puzzles available in order to write the solver.

The rest I'll leave to those who have written a solver.

But no, I don't think that it's cheating - you can still stick to conventional methods and checking as it suits you. Also, some solvers provide a check to make sure that the puzzle is a valid one before you begin solving, which can save a lot of heartache

Luna
lunababy_moonchild

Posts: 659
Joined: 23 March 2005

### Re: are solvers not cheating?

kat wrote:when you have worked it out right you will know it is correct so what use do you have for a solver?

What do you do if you get stuck? Some solvers can give you a hint.

The solver at this website can give you a vague hint (which 3x3 block to look at), a detailed hint (which digit you should be looking to place in that block), or solve the next step for you (telling you which rule it used).

www.sudokuhints.com

It's on online solver, nothing to download.
hawaiirob

Posts: 7
Joined: 30 May 2005

lunababy_moonchild wrote:but you have to know the best way of solving any of the puzzles available in order to write the solver.

I don't think so. Methods for solving these puzzles which are good for humans do not necessarily make particularly efficient solving algorithms for digital computers, and for this reason I doubt that you have to know a lot about solving Soduku by hand to write a competitive solver.

Sincerely,
Oudeis
Oudeis

Posts: 2
Joined: 30 July 2005

Oudeis wrote:
lunababy_moonchild wrote:but you have to know the best way of solving any of the puzzles available in order to write the solver.

I don't think so. Methods for solving these puzzles which are good for humans do not necessarily make particularly efficient solving algorithms for digital computers, and for this reason I doubt that you have to know a lot about solving Soduku by hand to write a competitive solver.

Sincerely,
Oudeis

Though it is simple to write a brute-force solver that will spit out the solution to a 9x9 Sudoku in an instant with the teensiest string of code, most of the challenge is to create software that solves in a "human-like way", using the type of logical tactics that people can and do use. The more they know about solving by hand, the better the results. A by-product is new tactics suitable for use by pencil-using solvers are expanded and created. The level of puzzle that can reasonably be solved by most carbon-based solvers is rising. Harder puzzles that were once scarce are in abundance and can be created on demand -- increasingly, to the exact specifications that the ludite puzzler wants.

Also, while brute force solving of a 9x9 puzzle is easy, as the size of the puzzle increases linearly, the time to complete a brute force search increase exponentially, quickly reaching a point where all the computer power in the universe will not help even with all the time in the universe. Although there is no getting past this limitation, they might be able to somewhat increase that limit by using 'smart' searches and incorporating logical tactics -- some of which may or may not be suitable for use by mortal solvers.

"Logic-based" solvers can also be useful to judge the relative difficulty of a puzzle to decide where you want to use your limited puzzle solving time -- brute force solvers are useless in this respect.

All of this increases the knowlege of Sudoku.

To the question of "cheating" -- that's completely contextual and subjective. If you use a solver -- any solver -- to find or even check your answer to a puzzle in a competition that specifically says not to use a computer or outside assistance, well, ok then. But if you use a solver to whip past the boring parts to get to the 'meat' of a puzzle -- don't want no salad, just give me the 'swordfish' -- well, ok then.
tso

Posts: 798
Joined: 22 June 2005