Monthly Archives: September 2012

Unsolvable 40 is Solved?


In the last post, Unsolvable 40 was staggered by a remarkable combination of coloring and LPO.  Only one pattern, 8b, was removed by LPO conflicts.  But other conflicts combined to force another pattern 8c to the color blue in an … Continue reading

Posted in Extreme Solving | Tagged , , , | 1 Comment

LPO vs Unsolvable 40


This post applies Limited Pattern Overlay, the sysudokie’s POM, to an Andrew Stuart Unsolvable, #40. The interplay of coloring and LPO patterns ties this beast up for the kill. Here is the grid as we apply LPO: My freeform LPO … Continue reading

Posted in Extreme Solving | Tagged , , , , , | Leave a comment

Toxic ALS in Unsolvable 40


Our struggle with Unsolvable 40 continues with a detailed walk through of the search for ALS toxic sets, and an analysis of the its stuck number ALS. Here is our grid with row ALS superimposed on a thin, as yet … Continue reading

Posted in Advanced Solving | Tagged , , , , , , , | 1 Comment

Advancing to LPO on Unsolvable 40


This post confirms the intractability of Andrew Stuart “Unsolvable #40” to SSOB  bv scan, X-panel analysis, coloring.  In preparation for Limited Pattern Overlay, a shortcut AIC reduces the number of patterns  for the number 8, and a coloring cluster is … Continue reading

Posted in Extreme Solving, Sudoku Toolware | Tagged , , , | 1 Comment