![]() ![]() ![]() ![]() Looking at the block on the lower left, I can see that the 1 in that block must occur in the first column. I’m gonna use the row/block and column/block technique to narrow them down further. Looking at just the 1s, these appear to be possible squares for ones: Here’s the puzzle at the point Margaret got stuck. If you’d like to try your hand at this puzzle, you’ll find the original here. Our first puzzle is from Margaret, who got stuck solving the daily Challenging puzzle from May 12th. If you want help with a particular Krazydad puzzle (especially puzzles that are easier than “Super Tough”), drop me a note, and I’ll troubleshoot your problem too! I’ve decided to devote the next few blog entries to puzzle solving techniques. Occasionally, I get mail from fans of the site who need help with a puzzle. | Comments Off on Sudoku Troubleshooter #2 – XY-Wing Of course this is contingent upon there only being one possible solution… Looking at column B, assume B4 is a 9, then A5, A9, B5 and B9 all have the same possibilities and there would be two possible solutions ergo B4 is not a 9 but a 2 and away you go. UPDATE: Stephen wrote me with an alternate breakthrough which makes use of the knowledge that the puzzle must have only one solution: In book 40 alone, puzzles 2,3 and 4 make use of it. Now the rest of the puzzle solves easily.Īs it turns out, XY-Wing crops up pretty frequently in the Tough puzzles. Once we’ve cleared the 1s out, it’s obvious that D3 must be 8. This means we can clear 1 as a possibility from cells D3, and E5.īoth of these cells are connected to both E4 and D5. This means that any cell that is simultaneously connected to both E4 and D5 cannot ever be 1 (because it would prevent both E4 and D5 from being 1). Since E4 can only be 2 or 7, either E4 or D5 must be 1. Think about the ramifications: If E4 is 2, then D5 must be 1. It is connected to cell E3 (which can be 1 or 7) and cell D5 (which can be 1 or 2). The root of the XY-wing is cell E4, which has 2 and 7 as possibilities. You can read about the XY-wing technique here. It turns out there is an XY-wing lurking in there. Normally, I’d be tempted to just substitute in a value and see what happens, but there is a more logical way to approach it. It looks nearly done, but the remaining cells look nearly intractable. Here’s the puzzle at the point where Margaret got stuck. ![]() This puzzle is also from Margaret, who got stuck on a Tough puzzle (Tough #4 from book 40). If you are stuck on a particular Krazydad puzzle, drop me a note, and I’ll use this space to help you out. These puzzles do not require more than one hypothesis by multiple choice.īy hypothesis we mean a supposition about the solution of a square in the absence of any logical reasoning.įor more information see: Main Menu General help.This is part of a series on puzzle solving techniques. Puzzles " Expert" are solvable by " Inclusion", " Exclusion, " Pairs exclusive" and " Multiple choice".Puzzles " Confirmed" are fully resolvable by " Inclusion" and " Exclusion" while admitting other methods.Puzzles " Beginner" are fully resolvable by " Inclusion" while while admitting other methods.Hexadoku printingįor maximum clarity and standardization, all our puzzles are printed in black and white, without shades of gray, color or images. Instead of using only the digits 1 to 9, the hexadoku sudoku uses the 16 digits of the hexadecimal base:Ġ, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F. The solving techniques are the same as for the 9x9 sudoku. Javascript is required to choose and print our hexadoku, 16x16 sudoku puzzles. ![]()
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