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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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 Posted: Sat May 10, 2008 4:53 am Post subject: 5/10/08 VH |
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| Code: | .---------------------.---------------------.---------------------.
| 2 1 789 | 37 348 789 | 5 6 349 |
| 4 3 79 | 1 6 5 | 2 79 8 |
| 5 #78 6 | 2 348 *789 | 379 479 1 |
:---------------------+---------------------+---------------------:
| 8 79 4 | 5 2 3 | 6 1 79 |
| 6 2 57 | 4 9 1 | 8 3 57 |
| 1 59 3 | 8 7 6 | 4 59 2 |
:---------------------+---------------------+---------------------:
| 7 #58 2 | 39 358 4 | 1 589 6 |
| 9 46 #58 | 67 1 #78 | 37 2 345 |
| 3 46 1 | 679 58 2 | 79 45789 459 |
'---------------------'---------------------'---------------------' |
I'll start with the w-wing on {7,8} in r3c2 and r8c6. the strong links are on 8, in r7c2 and r8c3. this w-wing eliminates the 7 in r3c6.
those same cells used in the W-wing also form a coloring ( skyscraper, kite, turbot fish, take your pick) elimination on the number 8 and eliminates 8 from r3c6 as well. |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sat May 10, 2008 5:11 am Post subject: |
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| Quote: | | I'll start with the w-wing on {7,8} in r3c2 and r8c6. the strong links are on 8, in r7c2 and r8c3. this w-wing eliminates the 7 in r3c6. |
I eliminated that same 7, but with an XY-Wing on 58-57-78 with pincer coloring. Then:
W-Wing on 37
XY-Wing on 78-79-89 with pincer coloring
W-Wing on 58 for the finishing blow
I found it more interesting and longer to solve than some others. |
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Victor
Joined: 29 Sep 2005
Posts: 207
Location: NI
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| Posted: Sat May 10, 2008 9:50 am Post subject: |
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Here's another way to look at Norm's 78s. It's a 3-step colouring chain in 8s from one #78 to the other via the 58s. So one of them must be 8 and the other must be 7. So they behave exactly like 'remote pairs': you can remove any 7 or 8 they both see, thus leaving just the 9 in r3c6.
Yes, interesting puzzle. Also at least a couple of ERs in there. |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sat May 10, 2008 12:57 pm Post subject: |
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I thought I was quite impressive here.
An x-wing on <5> took out the <5> in R9C9 which left the quad in R9 and triple in C8.
Then another x-wing on <8>.
Then I did one of them APE things (a first for me –high fives all round eh)
I looked at the <38> and <79> in Box 2. Can’t be a <37> or <39> or <78>. So it can only be an <89>.
Pls don't tell me I was wrong ! |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sat May 10, 2008 3:33 pm Post subject: |
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| cgordon wrote: | I thought I was quite impressive here.
An x-wing on <5> took out the <5> in R9C9 which left the quad in R9 and triple in C8.
Then another x-wing on <8>.
Then I did one of them APE things (a first for me –high fives all round eh)
I looked at the <38> and <79> in Box 2. Can’t be a <37> or <39> or <78>. So it can only be an <89>.
Pls don't tell me I was wrong ! |
Craig, I really couldn't re-create your position but I just configured the cells to match what you said was there. I won't tell you you're wrong. I think your APE reasoning is correct. However, when I proudly discovered APE, it was pointed out to me that it wasn't a necessary technique because almost every APE situation also contained an XY- or XYZ-Wing and I think there are two wings in your situation.
But I found out one time that it was useful because I missed the XY-Wing but did see the APE. So it's still mildly worthwhile.
Here's what I was so cleverly told:
| Quote: | APE is a monkey that you should not worry about.
I welcome any example of an APE exclusion that is not an XY... wing.
Keith |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sat May 10, 2008 3:58 pm Post subject: |
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| Quote: | | ......because almost every APE situation also contained an XY- or XYZ-Wing and I think there are two wings in your situation. |
Marty: You must be correct about APEs. I checked and there are indeed two xy wings with pivots in Box 2.
It's a shame really - because I find xy wings so dull and ordinary - even when I can find them. |
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crunched
Joined: 05 Feb 2008
Posts: 168
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| Posted: Sat May 10, 2008 4:18 pm Post subject: Re: 5/10/08 VH |
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| storm_norm wrote: |
I'll start with the w-wing on {7,8} in r3c2 and r8c6. the strong links are on 8, in r7c2 and r8c3. this w-wing eliminates the 7 in r3c6.
those same cells used in the W-wing also form a coloring ( skyscraper, kite, turbot fish, take your pick) elimination on the number 8 and eliminates 8 from r3c6 as well. |
I followed the w-wing pointed out here. I now believe I have learned what w-wings are.
I did not think I would have to learn to color. It appears that crayons are required for solving this.
Can you explain more about how the 8 was eliminated in r3c6? |
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Marty R.
Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA
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| Posted: Sat May 10, 2008 4:32 pm Post subject: |
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| Code: | .---------------------.---------------------.---------------------.
| 2 1 789 | 37 348 789 | 5 6 349 |
| 4 3 79 | 1 6 5 | 2 79 8 |
| 5 #78 6 | 2 348 *789 | 379 479 1 |
:---------------------+---------------------+---------------------:
| 8 79 4 | 5 2 3 | 6 1 79 |
| 6 2 57 | 4 9 1 | 8 3 57 |
| 1 59 3 | 8 7 6 | 4 59 2 |
:---------------------+---------------------+---------------------:
| 7 #58 2 | 39 358 4 | 1 589 6 |
| 9 46 #58 | 67 1 #78 | 37 2 345 |
| 3 46 1 | 679 58 2 | 79 45789 459 |
'---------------------'---------------------'---------------------' |
| Quote: | I followed the w-wing pointed out here. I now believe I have learned what w-wings are.
I did not think I would have to learn to color. It appears that crayons are required for solving this.
Can you explain more about how the 8 was eliminated in r3c6? |
Simple coloring involves a chain of strong links (must be an even number of cells) such that one end of the chain or the other must be a certain number, thus, any cell seeing both ends cannot be that number. If you look at the four-cell chain marked # it is evident that either r8c6 or r3c2 must be = 8. Since r3c6 sees both of those cells it can't be an 8. |
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cgordon
Joined: 04 May 2007
Posts: 769
Location: ontario, canada
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| Posted: Sat May 10, 2008 4:58 pm Post subject: |
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| Quote: | | Can you explain more about how the 8 was eliminated in r3c6? |
The 8 can also be eliminated using the x-wing in R18. |
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George Woods
Joined: 28 Mar 2006
Posts: 304
Location: Dorset UK
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| Posted: Sat May 10, 2008 5:28 pm Post subject: A different order to a solution! |
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I used th W wing on 58 to give 5 in box8 8 in box9 and after a few more moves an XY wing in boxes 1 and 2 (37& and the solution fell out.. |
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crunched
Joined: 05 Feb 2008
Posts: 168
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| Posted: Sat May 10, 2008 6:26 pm Post subject: |
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| Marty R. wrote: | | Code: | .---------------------.---------------------.---------------------.
| 2 1 789 | 37 348 789 | 5 6 349 |
| 4 3 79 | 1 6 5 | 2 79 8 |
| 5 #78 6 | 2 348 *789 | 379 479 1 |
:---------------------+---------------------+---------------------:
| 8 79 4 | 5 2 3 | 6 1 79 |
| 6 2 57 | 4 9 1 | 8 3 57 |
| 1 59 3 | 8 7 6 | 4 59 2 |
:---------------------+---------------------+---------------------:
| 7 #58 2 | 39 358 4 | 1 589 6 |
| 9 46 #58 | 67 1 #78 | 37 2 345 |
| 3 46 1 | 679 58 2 | 79 45789 459 |
'---------------------'---------------------'---------------------' |
| Quote: | I followed the w-wing pointed out here. I now believe I have learned what w-wings are.
I did not think I would have to learn to color. It appears that crayons are required for solving this.
Can you explain more about how the 8 was eliminated in r3c6? |
Simple coloring involves a chain of strong links (must be an even number of cells) such that one end of the chain or the other must be a certain number, thus, any cell seeing both ends cannot be that number. If you look at the four-cell chain marked # it is evident that either r8c6 or r3c2 must be = 8. Since r3c6 sees both of those cells it can't be an 8. |
Thanks. Nice explanation here. I understand it! |
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crunched
Joined: 05 Feb 2008
Posts: 168
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| Posted: Sat May 10, 2008 6:29 pm Post subject: |
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| cgordon wrote: | | Quote: | | Can you explain more about how the 8 was eliminated in r3c6? |
The 8 can also be eliminated using the x-wing in R18. |
I just don't see an x-wing here. Could you please elaborate? |
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keith
Joined: 19 Sep 2005
Posts: 3355
Location: near Detroit, Michigan, USA
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| Posted: Sat May 10, 2008 6:53 pm Post subject: |
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From here:
| Code: | +-------------------+-------------------+-------------------+
| 2 1 789 | 37 348 789 | 5 6 349 |
| 4 3 79 | 1 6 5 | 2 79 8 |
| 5 78 6 | 2 348 789 | 379 479 1 |
+-------------------+-------------------+-------------------+
| 8 79 4 | 5 2 3 | 6 1 79 |
| 6 2 57 | 4 9 1 | 8 3 57 |
| 1 59 3 | 8 7 6 | 4 59 2 |
+-------------------+-------------------+-------------------+
| 7 58 2 | 39 358 4 | 1 589 6 |
| 9 46 58 | 67 1 78 | 37 2 345 |
| 3 46 1 | 679 58 2 | 79 45789 459 |
+-------------------+-------------------+-------------------+ |
An X-wing on <5> in R58 takes out <5> in R9C9. Revealing a hidden pair <58> in R9.
After a little simplification, an XY-wing solves R3C2 as <7>, and the puzzle is done.
Keith |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sat May 10, 2008 7:28 pm Post subject: |
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this is the x-wing on 5 below
this is the hidden pair that keith pointed out
leads to this image below.
crunched, hi there.
in the image above is the x-wing on 8's
notice that there are only two 8's in rows 1 and 8, these two 8's are both in columns 3 and 6. this means that an 8 has to go in either column 3 and 6, in rows 1 and 8.
this means that any other 8's in columns 3 or 6 can't exist.
imagine putting an 8 in r3c6, what would happen in column 3?
| Quote: | | I did not think I would have to learn to color. It appears that crayons are required for solving this. |
an X-wing is a coloring pattern. it just happens to line up so nicely. other coloring patterns do not line up like an X-wing and can be more of a challenge to find. the VH's, at this point, do not require coloring but its fun to point out the interesting coloring patterns.
note: coloring in this example is usually considered "simple coloring" which normally confines coloring to a single digit AND these are often called "singles chains" as well.
Last edited by storm_norm on Sat May 10, 2008 8:10 pm; edited 1 time in total |
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TexCat
Joined: 07 Jul 2006
Posts: 32
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| Posted: Sat May 10, 2008 7:55 pm Post subject: |
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Too hard for me today. Though I did eventually see a solution with all the help here.
Norm -- what did you do with that 8 in R1C5? That's probably why we are having a hard time with x-wing. I see 3 8's in row 1. |
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storm_norm
Joined: 18 Oct 2007
Posts: 1741
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| Posted: Sat May 10, 2008 8:11 pm Post subject: |
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| TexCat wrote: | Too hard for me today. Though I did eventually see a solution with all the help here.
Norm -- what did you do with that 8 in R1C5? That's probably why we are having a hard time with x-wing. I see 3 8's in row 1. |
ok, I believe I corrected the grid. good eye, thanx. |
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crunched
Joined: 05 Feb 2008
Posts: 168
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| Posted: Mon May 12, 2008 1:47 am Post subject: |
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Those nice big demonstrative diagrammed squares explain it all!
Thanks Norm. |
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