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David
Joined: 02 Jun 2006
Posts: 58
Location: Bedford, UK
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 Posted: Sun Oct 01, 2006 2:22 pm Post subject: Question on type 2 UR's |
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Can somebody answer me this question;
123 1235
12 12
For the above example, is it possible to exclude the number 3 from any other cells on the top row ? |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sun Oct 01, 2006 5:37 pm Post subject: |
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| I am hardly a rectangle expert, but it looks like the exclusion could be made if in the top row, all the possibilities for "3" are confined to that row. |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sun Oct 01, 2006 6:04 pm Post subject: Re: Question on type 2 UR's |
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| David wrote: | Can somebody answer me this question;
123 1235
12 12
For the above example, is it possible to exclude the number 3 from any other cells on the top row ? |
No. The solution could be (for example)
and <3> must lie somewhere else in the row.
Some exclusions may be possible:
If there is a candidate pair <35> in some cell in the top row, you can eliminate <35> from the remaining cells in the row. The same holds true if the top cells are in the same 3x3 box, and there is a canidate pair <35> in the box. Here is the argument:
| Code: | 123 1235 35 . . .
12 12 |
To ensure uniqueness, either <1> or <2> must be missing in the solution of the first two cells in the row. One of them must be <3> or <5>, so the three cells contain all the possible occurrences of <35> in the row.
The same logic applies if you have something like
| Code: | 123 1235 345 45. . .
12 12 |
The first four cells contain all the occurrences of <345>.
The other type of reduction occurs if the only occurrences of <1> (or <2>) in the top line are on the corners of the rectangle. Then, <2> (or <1>) can be eliminated from the top two cells of the rectangle.
If <1> is a strong link in the top line, you get
Keith |
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David
Joined: 02 Jun 2006
Posts: 58
Location: Bedford, UK
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| Posted: Mon Oct 02, 2006 6:55 pm Post subject: |
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| Thanks for the replies guys, that helps |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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