Tag Archives: XY-chains

Andrew’s Solver Tames Worlds 200


This post walks through the “very  hard” part of the solution path taken by  Andrew Stuart’s Solver through puzzle 200 of The World’s Hardest Sudoku Book by authors unknown. This is a remarkable turn of events for a blog devoted … Continue reading

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Bean’s Extremely Hard I


A review of Rebecca Bean’s 600 Extremely Hard Sudoku Puzzles with Answers begins with the review table and two puzzles, 7-6 and 12-6. The collection is mostly basic, with the half of them solved by the slink marking bypass. Puzzle … Continue reading

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A Little Harder Ardson v2. 358


Next to last, and getting beyond the XY railway, is A.D. Ardson Very Hard, v.2 358. Here is the basic trace, including an X-wing in the close of line marking. The column 6-wing  was found in line marking closure, when … Continue reading

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Hodoku XY-Chains


As we explore Hodoku Chains and Loops (tech-chains.php) examples, here I contrast the premise starting, chain following school of Stephens/Hodoku, with the Sysudoku find-em-all technique of XY-rails. Also, a mathematically sensible order is suggested for remote pairs, as a Hodoku … Continue reading

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