![]() You can follow any responses to this entry through the RSS 2.0 feed.īoth comments and pings are currently closed.Ģ Responses to “Sudoku Troubleshooter #4 – XYZ-Wing” On Thursday, November 24th, 2011 at 8:49 pm and is filed under Puzzles. For the curious, the following puzzles contain an XYZ-Wing. It’s fairly rare, and only occurs in 8 of my tough puzzles, as compared to XY-Wing, which occurs 10 times more often. From here, the rest of the puzzle solves pretty easily.Īs I said, this particular configuration, in which D3 contains XYZ, and E1 contains XZ, and A3 contains YZ, enabling us to eliminate Z from a 4th cell which is connected to all three cells, is called an XYZ-Wing. Therefore, since this covers all the possible values for D3, F3 can’t ever be 4. If D3 is 7, then A3 must be 4, and F3 can’t be 4. If D3 is 5, then E1 must be 4, and F3 can’t be 4. Take a look at cell D3, and the effect it has on cell F3. XYZ-Wing is an advanced solving technique which is closely related to the more common XY-Wing, which I’ve covered in a previous column. In the next diagram, I’ve highlighed three cells which form an XYZ-Wing. If you’d like to try it yourself, you’ll find it here: This is a tough puzzle, book 85, puzzle #1. Here’s the puzzle that Michael got stuck on. am I missing something here or do I just need to guess? My question was is this a valid way of solving puzzles for you? As you will see I have gone through this puzzle attached and I can’t see a logical way to solve it. It seems like more recently you have been posting puzzles with no “logical” solution but that requires one to guess or work it out on the scratch pad. I have been going through a bunch of them and I have a question for you. I really enjoy your puzzles and I have advanced to your tough ones now. Good morning and an early happy thanksgiving. If you are stuck on a particular Krazydad puzzle, drop me a note, and I’ll use this space to help you out. They come in five levels of difficulty.This is part of a series on puzzle solving techniques. For more difficult puzzles see my collection of printable free sudoku puzzles. You will be able to solve the puzzle quickly now.Ĭongratulations on solving a very difficult Sudoku puzzle. Solve the naked single and the logjam is broken. When you remove the 4s, you now expose a naked single in (R7, C7). The cells circled in red may have the number 4 removed from them safely. Therefore, it is safe to eliminate the 4s from column 3 and column 7 except for the highlighted positions. We do know that it must reside in two of the four positions highlighted. At this point, we do not know which pair the 4 will reside in. Sudoku rules forbid any other combination. This means the 4 will reside in the pair (R2,C3) and (R5,C7) or in the pair (R2,C7) and (R5,C3). ![]() The two positions have to be diagonally opposites forming an X (hence the name). The number 4 can only appear in two of the four positions. These four positions are highlighted in grey. In row 5, the cells are (R5, C3) and (R5, C7). In row 2, the cells are (R2, C3) and (R2, C7). Each row has the number 4 in only two cells. In the example shown, an X Wing pattern occurs in row 2 and row 5. This candidate must reside in both rows and share the same two columns or vice versa. If these terms are not familiar, read my article Sudoku Tips for an illustrative guide.Īn X-Wing pattern occurs when two rows (or two columns) each contain only two cells that hold a matching candidate. You will need to solve naked singles, hidden singles, a naked pair (4,7) in row 7, a locked candidate (5) in column 7, and a naked triple (2,4,5) in column 1 first. If you have trouble getting to this position, follow the steps I have outlined in my article “How to Solve Sudoku” X-Wing”. You will need to partially solve the puzzle to reach the picture shown. ![]()
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