The New Sudoku Players' Forum

[jammaj]

I have just started playing Sudoku this week. One word:wow!

Anyway, today I tackled my first hard puzzle from this link:

http://www.dailysudoku.co.uk/sudoku/index.html

xxx xxx x89
7xx xx2 3xx
x1x xx3 2xx

8xx x36 7x2
xxx 9x5 xxx
9x1 28x xx3

xx9 3xx x5x
xx5 6xx xx4
28x xxx x3x

Here's what I came up with so far:

xxxxxxx89
79xxx23xx
x1xx9327x
854136792
xxx9x5xxx
9x128x5x3
xx932xx5x
xx56xxx24
28xxxxx3x

When I asked for a hint from the Draw(er), a 7 was filled into the last row

287xxxx3x

So my question is, why a 7?

Thanks!
jammaj, who needs to read up on X-wings and Swordfishes and who knows what all!!!!!

[simes]

"Disjoint subset".

In column 3, there are three cells (2,3)(3,3)(9,3) that have candidates of only 6, 7 or 8. Three cells, with only three candidates, means each cell takes a candidate, so you can eliminate those candidates for other cells in the column.

After that, there's only one cell in the column that can be a 7.

Tricky, but true!

[jammaj]

Many thanks, Simes! Tricky, but true works for me!!!

Also, thanks for the Sudoku tutorial on your website!

Enjoy!
jammaj

"Disjoint subset".

In column 3, there are three cells (2,3)(3,3)(9,3) that have candidates of only 6, 7 or 8. Three cells, with only three candidates, means each cell takes a candidate, so you can eliminate those candidates for other cells in the column.

After that, there's only one cell in the column that can be a 7.

Tricky, but true!

Simes
http://www.simes.clara.co.uk/programs/sudoku.htm