dailysudoku.com

[George Woods]

Have I found a xx in the "daily sudoku's" ability to solve? The sunday times normally defeats it. I enter it into draw, and then grade it, so that I can print it on a decent bit of paper. Anway true to form it graded it as too difficult-- So over breakfast I solve it- but no clever stuff. Why not? had I made a lucky guess by mistake? So back to Sudoku solving. It arrived at this "crunch point" and could progress no further!

002 876 900
100 429 000
000 153 000
080 791 360
700 268 005
061 534 070
020 687 000
010 942 007
079 315 600


My solution noted that Box1 is "attacked " by 678 in row 1 and by 678 in col 2 so r3 c1 and c3 as well as r2c3 are preoccupied with 67 and 8. That leaves r3c2 as 9 and so on ...... to solve the problem. How did the solver miss it?

[David Bryant]

Hi, George!

I didn't write the "draw" program, so I'm just guessing, but my guess is that "draw" looks for hidden pairs, and doesn't look for hidden triplets.

Maybe we can get samgj to offer us his perspective on this. dcb

[Dale]

Doh! I thought the program I wrote was finished... One of the subroutines finds, within a set of nine cells, digits whose "cell sets" are the same. If the number of cells in the cell set and number of digits having that cell set are the same, then stuff happens. But because the "7" in the first column eliminates r3 c1 from 7's cell set, the subroutine only sees 6 and 8 as two digits having the same three-cell cell set and ignores it.

If I enter the first column "7" last, the program solves it. Might work on the "draw" program, too.