mayres wrote:udosuk - you are ABSOLUTELY correct! I don't think you "guessed" at all.
Mike, you are ABSOLUTE correct about this bit too.
mayres wrote:I'd like to ask a few questions about the x-wing you suggested. I have read about the x-wing in various places and want to make certain I have the correct principle as it applies to this puzzle and others.
Are we talking about r5c1, r5c9, r9c1, and r9c9?
Yes. These are the 4 cells relevant to this move.
mayres wrote:If this be the case I'm wondering what the logic is in this puzzle for example. From what I can understand by reading the example given in this thread it appears that the next step is to eliminate all the "1's" from the other cells in columns 1 and 9. Is this correct?
Totally correct.
mayres wrote:I'm having a challenge understanding why at this step a 1 cannot be in r4c1 or r4c9? What is the logic versus just taking them out because of the x-wing present?
An easy way to see the logic is to visualise what would happen if r4c1=1. Then the 1s on r5 & r9 will be forced to be on r5c9 and r9c9 respectively. Thus we're forced to have two 1s on c9, a contradiction. Therefore r4c1 must not be 1.
mayres wrote:Is the principle that there must be the same number in all four corners with not other repeats of the number in the row, but the other number can be anything? Is it necessary for any of the four pairs to be identical? Does it only work with pairs?
The pairs aren't important here. Just focus on the
digit 1. The main point is there are exactly two 1s on the same columns on each of row 5 & row 9. Other digits can be completely ignored for this move. As a guide, take a look at the following board. All the information you need to know is in there.
- Code: Select all
. . . | . 1 1 | . 1 -1
. 1 1 | . 1 1 | . . .
. 1 1 | 1 1 . | . 1 .
-----------+-----------+-----------
-1 1 . | 1 . . | 1 . -1
#1 . . | . . . | . . #1
-1 . . | . 1 1 | . 1 .
-----------+-----------+-----------
. . . | . 1 1 | . . .
. . 1 | . . . | 1 . -1
#1 . . | . . . | . . #1
mayres wrote:Thanks to any words of wisdom you can provide to help in further understanding. Also, is it OK to continue to ask these kinds of questions here or should I be doing it somewhere else?
This is a good place to ask these kinds of questions. Whenever we have the time (and the mood
) we'll be glad to provide help to beginners and bring them up to speed. I do think there are other similar forums on the Internet for these questions but as long as you're comfortable here feel free to ask any questions you want.
