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Topic: Sudoku
Replies: 51   Last Post: Sep 26, 2005 3:12 AM

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 Arthur J. O'Dwyer Posts: 91 Registered: 12/13/04
Re: Sudoku
Posted: Aug 25, 2005 4:07 PM

On Thu, 25 Aug 2005, Simon Tatham wrote:
[...]
> Hmm. I suppose it could be seen that way, although that's not how I
> saw it. I saw it as a special case of a rather different pattern,
> which I currently describe as `mutual neighbour analysis'. Rather
> than being a chain of arbitrary length, this pattern involves
> finding two non-adjacent squares and a bunch of their mutual
> neighbours, and observing that placing a particular number in one of
> the end squares forces all the neighbours to take values which cause
> a contradiction in the other end square.

[...]
> If the 45 square has a 4 in it, [...] a problem. Hence, the 45 square
> can't be a 4, so must be a 5.

Tell me again how this is distinct from "backtracking"? Basically,

1. Fill in a value for cell X.
2. Fill in a value for cells Y, Z,... dependent on X.