I have to say thats it been a long time since I sat back and was amazed by what
people can do.
My knowledge of SQL is limited, whilst I recognise it is a functional language,
I had no idea you could solve Sudoku in it.
I take my hat off to the real experts. The downside of this is I now really,
really understand how little I know the language :)
Rob.
On 18 Jan 2014, at 17:50, Dan Kennedy <danielk1...@gmail.com> wrote:
>
> Beaten by minutes!
>
>
> /* The input suduko. */
> WITH RECURSIVE input(sud) AS (
> VALUES(
> '53 7 6 195 98 6 8 6 34 8 3 17 2 6 6 28 419 5
> 8 79'
> )
> ),
>
> /* A table filled with digits 1..9, inclusive. */
> digits(z, lp) AS (
> VALUES('1', 1)
> UNION ALL SELECT
> CAST(lp+1 AS TEXT), lp+1 FROM digits WHERE lp<9
> ),
>
> /* The tricky bit. */
> x(s, ind) AS (
> SELECT sud, instr(sud, ' ') FROM input
> UNION ALL
> SELECT
> substr(s, 1, ind-1) || z || substr(s, ind+1),
> instr( substr(s, 1, ind-1) || z || substr(s, ind+1), ' ' )
> FROM x, digits AS z
> WHERE ind>0
> AND NOT EXISTS (
> SELECT 1 FROM digits AS lp
> WHERE z.z = substr(s, ((ind-1)/9)*9 + lp, 1)
> OR z.z = substr(s, ((ind-1)%9) + (lp-1)*9 + 1, 1)
> OR z.z = substr(s, (((ind-1)/3) % 3) * 3
> + ((ind-1)/27) * 27 + lp
> + ((lp-1) / 3) * 6
> , 1)
> )
> )
>
> SELECT s FROM x WHERE ind=0;
>
>
>
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