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Systematic Sudoku

Tuesday, March 19th, 2013

John Welch writes an excellent blog for advanced Sudoku Solvers called Systematic Sudoku. Every Tuesday he posts a new detailed analysis of a tough puzzle, one of his goals being to understand the comparative difficulties of various sudoku publications. Sudoku difficulty is hard to measure and describe, and different publications (including this website) use different […]

Sudoku Troubleshooter #4 – XYZ-Wing

Thursday, November 24th, 2011

Troubleshooter #4: XYZ-Wing This is part of a series on puzzle solving techniques. If you are stuck on a particular Krazydad puzzle, drop me a note, and I’ll use this space to help you out. Michael wrote in an email: Dad, Good morning and an early happy thanksgiving. I really enjoy your puzzles and I […]

Sudoku Troubleshooter #3 – X-Wing

Monday, August 29th, 2011

This is part of a series on puzzle solving techniques. If you are stuck on a particular Krazydad puzzle, drop me a note, and I’ll use this space to help you out. This is a tough puzzle, book 7, puzzle 7. It was submitted by Stephen, who got stuck after solving 4 numbers, like so: […]

Sudoku Troubleshooter #2 – XY-Wing

Wednesday, August 24th, 2011

This is part of a series on puzzle solving techniques. If you are stuck on a particular Krazydad puzzle, drop me a note, and I’ll use this space to help you out. This puzzle is also from Margaret, who got stuck on a Tough puzzle (Tough #4 from book 40). If you’d like to try […]

Sudoku Troubleshooter #1 – Row/Column/Block

Tuesday, August 23rd, 2011

Occasionally, I get mail from fans of the site who need help with a puzzle. I’ve decided to devote the next few blog entries to puzzle solving techniques. 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! […]

An Index of Sudoku Strategies

Thursday, September 29th, 2005

Sudoku is a game of pure logical deduction, just like Kakuro and other Japanese number puzzles. Unlike games of luck such as card and bingo games, guessing is never required. I’ve now learned a number of methods for solving tough Sudoku puzzles by hand, including X-Wing, Swordfish, Jellyfish, Squirmbag, Turbot-fish, XY-Wing, XYZ-Wing, Conjugate Pairs, Bowman […]