# Category Archives: Stuart

web site and Logic of Sudoku

## Logic Justifies Aligned Triple AIC Hinges

This post takes on a challenge puzzle 17 which follows the Figure 30.1 of the previous post, in Andrew Stuart’s The Logic of Sudoku.   A boomerang ANL shows why aligned triple candidates are eligible to be AIC hinge partners. Logic … Continue reading

## Fleshing Out Stuart’s ALS Node Figure 30.1

Andrew Stuart’s The Logic of Sudoku, in a chapter on Almost Locked Sets, presents an example of an ALS node in a confirming Almost Nice Loop, as Figure 30.1. This post fills in the solution, before and after the series … Continue reading

## Completing CLEF for Unsolvable 197

This post notes how base candidate combinations of an exocet can be reduced in additional ways, then continues the exocet trials of Unsolvable 197 by means of Sysudoku Chute Lettering Exocet Filter.  This technique is, in part, a systematic way … Continue reading

## How the BARN Was Built

This post continues a report on the discovery of a practical human solving technique and the need to have it properly classified and named. This method has been credited to its author, known by his forum moniker as StrmCkr, on … Continue reading

## Please Give WXYZ Some Space

This post takes issue with recent redefinitions of the WXYZ-wing It suggests a name for Andrew Stuart’s update, apparently proposed by StrmCkr, and recalls the Bob Hanson’s Bent Naked N-set method in Student Assistant. The derivation of the toxic set … Continue reading

## Stuart’s Avoidable Rectangle

In The Logic of Sudoku, Andrew Stuart introduces a UR method in which corners on one side are known values, i.e. clues, and remaining candidates are prevented from forming a deadly rectangle with these clues.  This is his Avoidable Rectangle. … Continue reading

## Stuart’s Hidden UR

In Logic of Sudoku, Andrew Stuart describes a unique rectangle with only one bv corner.  The tell-tale naked pair is not there.  Stuart calls this formation a hidden UR, with good reason.  You have to find the bv candidates in … Continue reading

## Unit Forcing Chains

Here I explain why sysudokies pass on Andrew Stuart’s Dual Unit Forcing Chains.  We also examine a triple unit forcing chain from Unsolvable 40. As of this post, this statement continues  to appear  in Andrew’s sudowiki.org introduction to Unit Forcing … Continue reading

## Cell Forcing Chains

Here we examine forcing chains starting from all candidates in a cell.  When the number of chains is 2, there is nothing new.  Above that,  there is a new strategy to explore, which rivals LPO in complexity, but falls behind … Continue reading