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help with todays puzzle

 
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aplanells



Joined: 22 Jun 2006
Posts: 1

PostPosted: Thu Jun 22, 2006 3:27 pm    Post subject: help with todays puzzle Reply with quote

i need help with todays puzzle

I have
65-3-71-9
7-46913-5
39125--76
5-31769-2
-7--3--61
----29537
---76-2-4
------7-8
4-79-2653

The hint is in r9c2 a 1 but i cant get there
thanks
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Thu Jun 22, 2006 5:14 pm    Post subject: Reply with quote

I do these things strictly with pencil and paper, so I'm not looking at what you are. But I had the same numbers filled in as you, except I hadn't yet solved r5c5 for "3."

There is an X-wing on "2" in cols 13 and rows 58. This eliminates the "2" from r8c2, which opens up a Type 4 rectangle on "29" in boxes 47. That solves the "19" in box 9. r2c2 can then be solved for "2." Standard elimination techniques solve a bunch of cells, including r9c5 for "8", which takes care of the hinted-at r9c2.

After proceeding with basic stuff from there, a Type 1 rectangle on "45" opens up in boxes 5 and 8. After that, basic stuff completes the puzzle.
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Steve R



Joined: 24 Oct 2005
Posts: 289
Location: Birmingham, England

PostPosted: Thu Jun 22, 2006 7:02 pm    Post subject: Reply with quote

Most likely the hint used the X-wing for 8 based on rows 2 and 4. This eliminates 8 from r9c2 and the rest of the puzzle is straightforward.

Steve
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Blas



Joined: 19 Jul 2005
Posts: 8

PostPosted: Fri Jun 23, 2006 8:22 am    Post subject: 22 June puzzle Reply with quote

I read the posts with interest cos I am still struggling and grateful for any help, please!

1 - How is the 3 in r5c5 deduced?
2 - Everytime i think I have grasped X-wings, I realize I haven't. I thought the number had to be unique for the columns? But I have an alternative "2" in r1c3.
3 - Just re-looked at the bit about the x-wing on 8s on r24c28 and see that x-wing but not the one on "2"s.

---blas
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David Bryant



Joined: 29 Jul 2005
Posts: 559
Location: Denver, Colorado

PostPosted: Fri Jun 23, 2006 11:52 pm    Post subject: More about "X-Wings" Reply with quote

blas wrote:
1 - How is the 3 in r5c5 deduced?


It beats the hell out of me. It happens to be irrelevant, anyway, because even without the "3" at r5c5, the "X-Wing" on 8's still works, and the 3 at r5c5 falls out soon after that.

blas wrote:
3 - Just re-looked at the bit about the x-wing on 8s on r24c28 and see that x-wing but not the one on "2"s.


I couldn't find an "X-Wing" on 2's at this stage, either. I re-read Marty's description, and it seems he has overlooked the possibility of a "2" at r1c3. Of course, he gets to the right conclusion anyway, because if we trace the eliminations made possible by the "X-Wing" on the 8's we have this chain of inference:

r9c2 = 1 ==> r9c5 = 8 ==> r1c5 = 4 ==> r4c8 = 4 ==> r4c2 = 8 ==> r2c2 = 2 ==> r8c2 <> 2

So Marty's right, that there can't be a "2" at r8c2, but I sure don't see an X-Wing on the 2's to get there. dcb
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Charles



Joined: 31 Mar 2006
Posts: 8
Location: Lawton, Oklahoma, USA

PostPosted: Sat Jun 24, 2006 5:55 am    Post subject: June 22, 06 Very hard Reply with quote

I, too, cannot see the three at R5C5 in the original post. I looked at this one a long time and overlooked the "8" X-Wing because I kept being drawn to the multiple Unique Rectangles in this puzzle. Has anyone devoted some thought to the "overlapping of URs". i.e could all of the possible "necessary choices" brought about by the URs somehow lead to contradictions which could possibly lead to a logical single choice or chain of choices for all of the URs. Naturally, this is leading to some serious investigation. A disclaimer - I have not read about Unique Rectangles beyond the description. Enjoyed the discussion. Charles
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Chuck B



Joined: 24 Jun 2006
Posts: 24

PostPosted: Sat Jun 24, 2006 4:27 pm    Post subject: A 'coloring' solution Reply with quote

Steve's X-wing solution is elegant.

A slightly longer solution illustrates simple coloring.

From this point:
Code:

 *------------------------*
 | 6 5 . | 3 . 7 | 1 . 9 |
 | 7 . 4 | 6 9 1 | 3 . 5 |
 | 3 9 1 | 2 5 . | . 7 6 |
 |-------+-------+-------|
 | 5 . 3 | 1 7 6 | 9 . 2 |
 | . 7 . | . . . | . 6 1 |
 | . . . | . 2 9 | 5 3 7 |
 |-------+-------+-------|
 | . . . | 7 6 . | 2 . 4 |
 | . . . | . . . | 7 . 8 |
 | 4 . 7 | 9 . 2 | 6 5 3 |
 |-------+-------+-------|
the corresponding '8' candidate pattern is:
Code:
 *-----------------------*
 | . . 8 | . 8 . | . 8 . |
 | . 8 . | . . . | . 8 . |   <---+-  Steve's X-wing
 | . . . | . . 8 | 8 . . |       |
 |-------+-------+-------|       |       
 | . 8 . | . . . | . 8 . |   <---+
 | 8 . 8 | 8 8 8 | 8 . . |
 | 8 8 8 | 8 . . | . . . |
 |-------+-------+-------|
 | 8 8 8 | . . 8 | . . . |
 | . . . | . . . | . . # | (# denotes the 8 already placed):
 | . 8 . | . 8 . | . . . |
 *-----------------------*

To set up coloring, notice that C4's 8 must occupy R5 or R6, eliminating 8 as a candidate from R5C5 and R5C6, yielding this pattern:
Code:
 *-----------------------*
 | . . 8 | . 8 . | . 8 . |
 | . 8 . | . . . | . 8 . |
 | . . . | . . 8 | 8 . . |
 |-------+-------+-------|
 | . 8 . | . . . | . 8 . |
 | 8 . 8 | 8 . . | 8 . . |
 | 8 8 8 | 8 . . | . . . |
 |-------+-------+-------|
 | 8 8 8 | . . 8 | . . . |
 | . . . | . . . | . . # |
 | . 8 . | . 8 . | . . . |
 *-----------------------*
(at this point, coloring in '4' yields R5C5 = 3, but it's not needed)

Now follow two conjugate chains starting from R3C6: R3C7/R5C7/R4C8/R4C2 and R7C6/R9C5/R9C2.

R4C2 and R9C2 are different 'colors', forming a conjugate pair that eliminates the other 3 8's in C2 as candidates:

*----------------------*
| _ _ 8 | _ 8 _ | _ 8 _ |
| _ 8 _ | _ _ _ | _ 8 _ |
| _ _ _ | _ _ 8 | 8 _ _ |
|------+-------+-------|
| _ 8 _ | _ _ _ | _ 8 _ |
| 8 _ 8 | 8 _ _ | 8 _ _ |
| 8 8 8 | 8 _ _ | _ _ _ |
|-------+-------+-------|
| 8 8 8 | _ _ 8 | _ _ _ |
| _ _ _ | _ _ _ | _ _ # |
| _ 8 _ | _ 8 _ | _ _ _ |
*----------------------*

(sorry 'bout the format change; can't do colors in 'code')

As with the X-wing, the puzzle collapses from this point.

Cheers!
Chuck
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Chuck B



Joined: 24 Jun 2006
Posts: 24

PostPosted: Sat Jun 24, 2006 5:13 pm    Post subject: Re: 22 June puzzle Reply with quote

Blas wrote:
How is the 3 in r5c5 deduced?

From this point:
Code:
 *-----------------------*
 | 6 5 . | 3 . 7 | 1 . 9 |
 | 7 . 4 | 6 9 1 | 3 . 5 |
 | 3 9 1 | 2 5 . | . 7 6 |
 |-------+-------+-------|
 | 5 . 3 | 1 7 6 | 9 . 2 |
 | . 7 . | . . . | . 6 1 |
 | . . . | . 2 9 | 5 3 7 |
 |-------+-------+-------|
 | . . . | 7 6 . | 2 . 4 |
 | . . . | . . . | 7 . 8 |
 | 4 . 7 | 9 . 2 | 6 5 3 |
 *-----------------------*
the only candidates for R5C5 are 3, 4 and 8.

The 8 for the central box has to be in column 4, so R5C5 cannot be '8'.

Next look at the '4' candidate pattern:
Code:
 *-----------------------*
 | . . . | . 4 . | . 4 . |
 | . . # | . . . | . . . |  <-- '#' denotes a known 4
 | . . . | . . 4 | 4 . . |
 |-------+-------+-------|
 | . 4 . | . . . | . 4 . |
 | . . . | 4 4 4 | 4 . . |
 | . 4 . | 4 . . | . . . |
 |-------+-------+-------|
 | . . . | . . . | . . # |
 | . . . | 4 4 4 | . . . |
 | # . . | . . . | . . . |
 *-----------------------*
Follow the chain R1C5->R1C8->R4C8->R5C7 and you can see that R1C5 and R5C7 form a conjugate pair.

Since one of them must be a '4', R5C5 cannot be '4'.

The only candidate left for R5C5 is 3. Voila! Wink

Cheers!
Chuck
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TKiel



Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI

PostPosted: Sun Jun 25, 2006 3:20 pm    Post subject: Reply with quote

Chuck B,

There has been some discussion about making individual numbers contained in a grid different colors but nobody could figure out how to do it. Congrats on figuring it out, it sure makes following some explanations much simpler. How do you do it, if you wouldn't mind sharing?
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Marty R.



Joined: 12 Feb 2006
Posts: 5770
Location: Rochester, NY, USA

PostPosted: Sun Jun 25, 2006 4:10 pm    Post subject: Reply with quote

TKiel wrote:
Chuck B,

There has been some discussion about making individual numbers contained in a grid different colors but nobody could figure out how to do it. Congrats on figuring it out, it sure makes following some explanations much simpler. How do you do it, if you wouldn't mind sharing?

Tracy, I'm not Chuck, but it appears that it can be done by using the Font colour option that lies beneath the Bold, Italic, Underline and Quote options.


--8--8--8--8
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Chuck B



Joined: 24 Jun 2006
Posts: 24

PostPosted: Sun Jun 25, 2006 4:34 pm    Post subject: Editing digit color Reply with quote

Thanks, Tracy!,

When composing the message, I just selected the digit I wanted to color and applied the 'Font colour' option above the edit box. Unfortunately, you can't do that inside of a code block, and I couldn't figure out how to invoke a fixed font outside of a code block, so it was a challenge to achieve grid spacing that wasn't totally unreasonable.

By way of example, this red 8 and green 4 are done like this:
Code:
... red [color=red]8[/color] and green [color=green]4[/color] are done like...

I also played with hex color values to improve legibility on my monitor. For example, this tones down the red 8 a bit:
Code:
...tones down the red [color=#AA0000]8[/color] a bit.


You can also tweak the color in hex if you wish.
Code:
... tweak the [color=#AA8800]color[/color]...


Cheers!
Chuck
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TKiel



Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI

PostPosted: Sun Jun 25, 2006 4:36 pm    Post subject: Reply with quote

Marty R.,

Can you get it to do that inside the grid? I tried in my reply to Maggie Rose about 'x-wings, xy-wings' (which I noticed you beat me to, darn forum posting delay) but wasn't able to accomplish it.
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TKiel



Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI

PostPosted: Sun Jun 25, 2006 4:41 pm    Post subject: Reply with quote

Chuck B,

So the post with the colored numbers was not really inside a copy & paste grid, it was all stuff that was entered manually?
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Chuck B



Joined: 24 Jun 2006
Posts: 24

PostPosted: Sun Jun 25, 2006 4:50 pm    Post subject: Reply with quote

TKiel wrote:
Chuck B,

So the post with the colored numbers was not really inside a copy & paste grid, it was all stuff that was entered manually?


That's correct, Tracy. Styles aren't implemented inside a 'code' block, and there is unfortunately no 'fixed font' style outside of the 'code' block.

<sigh>

Cheers!
Chuck
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TKiel



Joined: 22 Feb 2006
Posts: 292
Location: Kalamazoo, MI

PostPosted: Sun Jun 25, 2006 4:59 pm    Post subject: Reply with quote

Chuck B wrote:
<sigh>


Couldn't agree more.

And I retract my congrats for discovering how to do it in the grid and extend it for having the patience to enter it manually so it looks as good as a grid. Very Happy
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Chuck B



Joined: 24 Jun 2006
Posts: 24

PostPosted: Sun Jun 25, 2006 5:06 pm    Post subject: Reply with quote

TKiel wrote:
And I retract my congrats for discovering how to do it in the grid and extend it for having the patience to enter it manually so it looks as good as a grid. Very Happy


Ah, the logic of a genuine Sudoku addict... I love it! Laughing

All the best!
Chuck
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