dailysudoku.com

Captain Pete · Joined: 09 Jun 2007 Posts: 55 Location: Oley, PA

I'm stuck. What technique gets me to the next number?

keith · Posted: Tue May 05, 2009 1:56 pm Post subject:

The candidate <5> in R5C1 does not belong.

After that, I think you need a chain. I do not see any simple named pattern.

Keith

arkietech · Posted: Tue May 05, 2009 3:17 pm Post subject:

Marty R. · Posted: Tue May 05, 2009 3:51 pm Post subject:

Alternatively, an M-Wing on the 58s in boxes 36 eliminates the same 8 as the ER.

Captain Pete · Joined: 09 Jun 2007 Posts: 55 Location: Oley, PA

Architech, Thanks for the reply. I've just been reading up on ERs, and I'm trying to use this puzzle as a tutorial. I see the strong link in row 3, but I can't see the ER. In your response, you identified two cells with #. What do those cells represent? In using the ER technique, is it necessary to screen each box for each number?

Marty R. · Posted: Tue May 05, 2009 5:08 pm Post subject:

An ER is where a number exists in just two lines within a box. Where the lines intersect is the ERI (Empty Rectangle Intersection). In this case the ERI is r5c8. The ERI needs to see one number of a strong link, the 8s in row 3 in this case. Any cell seeing both the ERI and the second half of the strong link (r5c1 in this case) can't contain the number.

arkietech · Posted: Tue May 05, 2009 7:31 pm Post subject:

Captain Pete,

Marty's answer was better than mine. I find er'[s by the logic of -- if this is on then this is off. The #'s are off if either r3c8 or r5c7 is on.. This is how I spot er's. I hope I have not confused you.

Captain Pete · Joined: 09 Jun 2007 Posts: 55 Location: Oley, PA

Thanks to all. Can the ERI contain one of the numbers in the comlementary strong link? For example, in this puzzle if the strong link contained a 4, would the 4s in box 7 constitute a ER with 345 being the ERI?

And, what prompts you to look for a specific number. in this case 8. Is there a tipoff of some kind?

M-wing, Oh no....

storm_norm · Joined: 18 Oct 2007 Posts: 1741

ER is a HINGE
as it relates to the candidates in a particular Box

notice how the 8's in row 3 are conjugate. both can't be false.
if the 8 in r3c1 is true, then the 8 in r5c1 can't be true.

now, the tricky part.

if 8 in r3c1 isn't true, then the 8 in r3c8 is true
then follow the hinge around
8 in r46c8 not true
8 in r5c7 true
and it points at the 8 in r5c1. that 8 can't be true.

so in both situations, the 8 in r5c1 can't be true.

another one...
this is Danny's "puzzle NR-005"

if you want to be imaginative with the hinge,
imagine using colors to label the 8's in row 4, red and green.
the HINGE allows the 8 in r4c6 to SEE AROUND THE CORNER. Cool

now that the 8 in r4c6 can see around the corner at the 8 in r1c1
the 8 in r1c1 can now see two colors.
in the world of coloring, if a candidate can see two colors, its toast.

Marty R. · Posted: Wed May 06, 2009 12:27 am Post subject:

Captain Pete · Joined: 09 Jun 2007 Posts: 55 Location: Oley, PA

I think I have it. Thanks to all!

tlanglet · Posted: Wed May 06, 2009 12:17 pm Post subject: