dailysudoku.com

[Mike]

Please help with logic for the October 24, 2005 hard puzzle. This is where I hit a wall . . .

470 203 900
060 810 020
021 079 500

500 001 000
200 000 005
000 700 006

702 900 450
090 547 032
054 102 079

Thanks for your help !

[Lulu]

I'm having problems working out how you got a 2 in r8c9 because at this position there are still 2 options for 2 in box 9 it could also be at r8c7.

Otherwise:-
Look at r8c3 this can only be an 8 because the 6 in column 3 must be at either r4 or r5 to satisfy box 4.

r1c3 5 is the only option

You should be able to complete box 2 from this stage.

See how you go

Lulu

[David Bryant]

[Lulu]

Silly me! I hadn't mapped out all the pairs at this time only marked the obvious placings.

[Glassman]

Mike — I don't know what this is called, as I am new to this forum and the terminology, but there is one of this compiler's favourite helpful hints in this elegant puzzle, which I saw as soon as I looked at it. Two numbers, here 6 and 7, on intersecting rows and columns, helpfully isolated to highlight them. See what this tells you about the box where they intersect, and then work it through.

Glassman

[Mike]

Thanks all for trying to find the logic thread in this puzzle.

For Glassman - I'm not sure where to find the intersection strategy published by the author of the puzzle . . . could you point me in the right direction? Also, which 67's are you referring to?

[Mike]

Lulu - your second comment is right on and now I can continue. Thanks so much!!

[David Bryant]

[Glassman]

[Mike]

David and Glassman,

I understand this logic and had isolated 67 with other possibilities to r4c3 and r5c3. This is a nifty way to reduce the possibilities further. Lulu's logic provided the jump which produced a 7 in r4c9 and therefore set 6 in r4c3 and 7 in r5c3.

Thanks for your thoughts,

Mike

[Mike]

This is my third day attempting SuDoku and I am totally enjoying these logic mazes !! Thanks for all your help. [/b]