Tag Archives: uniqueness methods

Absolutely Nasty4 Snaps II


One post wasn’t enough, so this is the second featuring highlights from the sysudokie review of Frank Longo’s Absolutely Nasty Level 4 collection. X-chains are normally denizens of the X-panels, but in AbsNasty4 #21, one was caught in line marking … Continue reading

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The Unique Rectangle


Here I will summarize for you the variations of the unique rectangle method, UR for short, as detailed in  the most complete sources I know of, the http://www.sudocue.net  solving guide, and  Andrew Stuart’s Logic of Sudoku.  Later posts will bring additional UR … Continue reading

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Mashing the BUG


Bivalue Universal Grave, the uniqueness method, requires knowledge, or at least absolute faith, that the puzzle has a single solution.  Coloring is a powerful analysis tool for the near BUG situation, making such knowledge unnecessary. A happy and prosperous New … Continue reading

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Stuffing Your Stocking


The resulting cluster extension leaves nothing but clues, bv and a single cell with three candidates,  a multiple solution situation the Sudoku community labels  BUG + 1. BUG stands for  Bi-Value Universal Grave, the reduction to clues and bv alone, … Continue reading

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Forcing Chains in Sue de Coq Analysis


In this post, the classical forcing chain and a sysudokie endorsed application are demonstrated on a multiple solution puzzle. An underlying assumption made in solving a Sudoku puzzle is that it has one and only one solution.  Some composers offer … Continue reading

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