Tag Archives: XY-wing

The World’s Most Over-Titled Sudoku Book


This post starts the review of World’s Hardest Sudoku Book, tracing Very Hard 25, the only one rated a 1.00. The review will cover the highest rated 10, taking the rating down to 0.90. The lowest of the 200 is … Continue reading

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Decoding Hodoku Chain Notes


This post comments on the first part of the Hodoku “Chains and Loops” page. It reveals the premise dependent view of chains to be based on computer coding, and unsuited for human solving advice. It explains Hodoku’s chain notations as … Continue reading

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Hodoku’s Limited XYZ Wings


In this post reviewing the Hodoku Wings page linked under Techniques, we see how an expert programmer can go wrong in explaining how to recognize where a technique applies and why it works . The omission of irregular wings is … Continue reading

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Wings and Chains With the Gordon Guide


This post reviews the Chapter 9 of Peter Gordon’s Sudoku Guide, entitled Forcing Chains and Grid Coloring. The guidance is very limited, and what there is, promotes guessing as opposed to solving by logic. This verdict is confirmed in the … Continue reading

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Bent Naked What?


Here I object to Bob Hanson’s use of the XY-wing and the XYZ-wing, in Sudoku Assistant – Solving Techniques, to introduce his more complicated concept of “bent naked subsets”. This treatment limits the wings to unit based links.  Also I’m … Continue reading

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The X-Panel and X-Chains


We will now be leaving methods relying on the bv map as the primary visual aid. With puzzles that survive these methods,   we need to remember that the bv map file remains an important resource.  With every clue or candidate … Continue reading

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XY-Chains


This post explains the XY-chain, the most specific, easy to spot, and prolific of Alternating Inference Chains. It includes what many call the XY wing, as the shortest possible XY-chain. One XY-chain can generate multiple toxic candidate pairs. An XY-chain … Continue reading

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