## Extreme puzzle from Playr.co.uk

Everything about Sudoku that doesn't fit in one of the other sections

### Extreme puzzle from Playr.co.uk

With the discussion on where to post published vs. unpublished puzzles, thought I'd put this up here. Extreme Puzzle off Playr for 4/7/08. Here's the original puzzle and PM's after STSS:

Code: Select all
`. . . | 4 2 . | . . .. . 6 | . . . | 7 5 .. 4 . | . . 5 | 2 6 .------+-------+------. . . | . 1 7 | . 3 .. . 5 | 8 . 4 | 6 . .. 3 . | 5 6 . | . . .------+-------+------. 6 2 | 3 . . | . 4 .. 1 7 | . . . | 9 . .. . . | . 9 2 | . . .57    57  1389 | 4  2 6 | 13 89 138912    29  6    | 19 8 3 | 7  5  4   138   4   1389 | 19 7 5 | 2  6  1389---------------+--------+-----------6     89  489  | 2  1 7 | 45 3  589 127   279 5    | 8  3 4 | 6  79 129 12478 3   148  | 5  6 9 | 14 78 128 ---------------+--------+-----------9     6   2    | 3  5 1 | 8  4  7   35    1   7    | 6  4 8 | 9  2  35  3458  58  348  | 7  9 2 | 35 1  6   `

I've found a single forcing net that reduces this puzzle to singletons (I set out looking for eliminations in the colored 3's and r1c7 looked promising):

r1c1-7-r1c2=7=r5c2=2=r2c2-2-r2c1=2=r5c1 (with r1c1-7-r5c1)... continues with r5c1=1=r5c9-1-r1c9 (with r2c1-1-r1c3)... continues with r1c9=1=r1c7

with

r1c1-5-r8c1=5=r8c9=3=r9c7. Together these nicely force r1c7<>3, which reduces this Extreme puzzle to Singletons.

The first "chain" is pretty messy; I'm wondering if anyone can find a more elegant, 1 or 2 step solution?

Cheers...

- drac

Shoot, hit Submit instead of Preview... cleaned up mistakes. Also adding note that the forcing net starting from r1c1, if extended a bit, cancels out other value s(such as r5c3<>8 and, more obviously r4c7<>3), but I left that out. It's messey enuf and these are not needed to crack the puzzle.
Draco

Posts: 143
Joined: 14 March 2008

Code: Select all
`1-r1c7-3-r9c7-5-r9c2-8-r4c2-9-r2c2-2-r2c1-1-(ER.in.b4)-1-r6c7=1=r1c7 => r1c7<>3`
Last edited by daj95376 on Wed Apr 09, 2008 2:25 am, edited 3 times in total.
daj95376
2014 Supporter

Posts: 2624
Joined: 15 May 2006

Nicely done; thanks Danny!
Draco

Posts: 143
Joined: 14 March 2008