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 to exploit the crossing line constraints of the Junior Exocet approach reported on the EnjoySudoku forum by David P. Bird.

Unsv 197  chute letHere again is the grid with non-base candidates removed by chute lettering.

Unsolvable 197 illustrates other  interesting possibilities for trial reduction.  The  Single Alternate Sue de Coq describes the contents of as  either 8(2+7)(5+9),  or the naked pair np59.  The Sue de Coq term confirms 13c4 and the np term, 1r3c6. That trial is deferred here, but with either term, or either 1 being true, both bases contain  (2+7)(5+9), i.e. 27 and 59 are not possible.  We missed that one.  The details remind us that base digit restrictions can also come from APE.

Unsv 197 29 57 row sitesPicking up on the failure of double exocets blue 2&7and green 5&9 last week, next up is blue 2&9 and green 5&7. This set is a bit simpler because, with a base digit of 7, target 1 cannot be 2.

 

The single color combination tables:

Unsv 197 3 one colors

Both green target placementsUnsv 197 two 9257 exocets are set up for trial:

 

 

Unsv 197 remote pairThe left one reveals the core slipperiness  of Unsolvable 197 with a tight little clique of 348 candidates, but a remote pair exposes its contradiction in a collapse.

Unsolvable 197 doesn’t much care which green targets you choose, bringing you the same cast of characters.

 

 

 

Unsv 197 wing and ANLBut this time, a 384-wing with a forcing chain victim, plus a simple 8-chain almost nice loop gives up the solution.

How did it go for you?

Next time, we peer over David P. Bird’s shoulder at his comment length Junior Exocet 197 solution, explain what his JE rules are really doing, and suggest how these rules, and the Exocet itself, could be more clearly expressed as a trial.

 

 

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About Sudent

My real name is John Welch. I'm a happily married, retired professor (computer engineering), timeshare traveling, marathon running father of 3 wonderful daughters and granddad to 7 fabulous grandchildren. The blog is about Sudoku solving. It covers how to start, basic solving to find candidates efficiently, and advanced solving methods in an efficient order of battle. It is about human solving methods, not computer solving.
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