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.
Here 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.
Picking 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:
Both green target placements are set up for trial:
The 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.
But 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.