Need help with one digit

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Need help with one digit

Postby Luch » Sat Mar 09, 2013 3:12 pm

Hi! 3 has to be in r2c1. I can't understand why. Could someone explain it in plain English? Thanks in advance!
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Re: Need help with one digit

Postby JasonLion » Sat Mar 09, 2013 4:21 pm

All of the cells in block 1 that can contain 3 are also in row 2. Since one of the cells in block 1 must contain 3, no other cell in row 2 can contain 3. In particular, R2C5 can not contain 3.

It takes several additional moves from there before it is possible to tell which of R2C1 and R2C3 contains 3.
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Re: Need help with one digit

Postby daj95376 » Sat Mar 09, 2013 5:59 pm

Given that you haven't resolved three much simpler steps, I doubt that a complex step for r2c1<>7 will be of any benefit to you.
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Re: Need help with one digit

Postby Luch » Sun Mar 10, 2013 2:05 pm

daj95376 wrote:Given that you haven't resolved three much simpler steps, I doubt that a complex step for r2c1<>7 will be of any benefit to you.
Why scare people away? If it's not me but maybe some of them have potential to become great players too.
Could you please reconsider and help here?
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Re: Need help with one digit

Postby JasonLion » Sun Mar 10, 2013 2:19 pm

I believe that daj95376's point is that you are asking the wrong question. You have quite a bit of work to do before you worry about R2C1 being 3. For example, did you understand my explanation for why R2C5 can not contain 3? Have you spotted the two other locked candidates that are present in the grid? Do you know anything about the Sashimi X-Wing or Skyscraper techniques? Can you spot the two occurrences of Sashimi X-Wing/Skyscraper that are present in the grid? Only after you master those things, and a few others, is it time to move on to the contents of R2C1.

Handy puzzle string: ..24.6.93.1.2.94684698..2..27..4.6.99...6..4264192..37.26.94.8..945...265..6.29.4
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Re: Need help with one digit

Postby Luch » Sun Mar 10, 2013 3:14 pm

The screen I've posted was the SadMan's advice for the next step. So it made me totally confused.
No, I had not mastered the Sashimi X-Wing or Skyscraper techniques. I'll get there.
Thanks for your reply.
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Re: Need help with one digit

Postby Luch » Sun Mar 10, 2013 3:22 pm

JasonLion wrote: For example, did you understand my explanation for why R2C5 can not contain 3? ...
Handy puzzle string: ..24.6.93.1.2.94684698..2..27..4.6.99...6..4264192..37.26.94.8..945...265..6.29.4

Yes, I did. I do four star sudoky for a while now.
Don't know what that puzzle string.
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Re: Need help with one digit

Postby JasonLion » Sun Mar 10, 2013 5:54 pm

The explanation I gave initially is what SadMan's app would have been hinting about. If you look at the cell highlight colors you can see that R2C5 has one highlight color, while both R2C1 and R2C3 share the other highlight color. That means that R2C1 and R2C3 were being treated in the same way. If it was going to tell you to place a 3 in R2C1 then that cell would have had it's own unique highlight color.

The puzzle string I gave is your puzzle in a standard format so that others helping you can input your puzzle into their programs. The image you posted is very clear and easy to read, but is not so helpful for inputing into programs.

This puzzle is a rather complex puzzle. I would call it medium difficulty, because we deal with an exceedingly wide range of difficulties here on the forum, but most newspaper puzzle players would call it exceedingly difficult. Fully solving it will require techniques like Sashimi X-Wing or Skyscraper or something even more complex/difficult. I'm not sure exactly what daj95376 had in mind to demonstrate that R2C1 is 3 in a single step, but it has to be something an order of magnitude more complex than a Sashimi X-Wing.
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Re: Need help with one digit

Postby JC Van Hay » Mon Mar 11, 2013 10:19 pm

Hi Luch, I have too many comments to say about this puzzle. So allow me to proceed step by step according to your interest.
First comment :
Even if I don't see the connection between your picture and your question, I understand why 3 has to be in r2c1 and I can explain it in plain English.
However, I am convinced you can do it all by yourself if I say that r2c1=7 would lead to an invalid puzzle! Post your answer and I will post mine for comparison.
Best Regards, JC.
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