(It has a couple additional candidate removals using other strategies before resorting to Exocet but is essentially the same situation.)

- Code: Select all
`002080067670000800000670000006000780020016054005000612061000405008050106457361298`

+----------------+----------------+-------------+

| 1359 139 2 | 149 8 349 | 359 6 7 |

| 6 7 349 | 1259 239 2359 | 8 24 139 |

| 13589 1389 349 | 6 7 239 | 359 24 139 |

+----------------+----------------+-------------+

| 139 1349 6 | 259 2349 2359 | 7 8 39 |

| 78 2 39 | 78 1 6 | 39 5 4 |

| 3789 3489 5 | 79 349 3789 | 6 1 2 |

+----------------+----------------+-------------+

| 239 6 1 | 2789 29 2789 | 4 37 5 |

| 239 39 8 | 247 5 2479 | 1 37 6 |

| 4 5 7 | 3 6 1 | 2 9 8 |

+----------------+----------------+-------------+

It gives these eliminations:

(1359)JE2:r1c12.r2c4,r3c7 (cover houses for (9) are r5 & c4 )

=> r2c4 <> 2 (non-base digit in target cell)

=> r2c4 <> 5 (base digit missing from mirror node)

=> r2c4 <> 9 (target cell is a non-'S' cell for (9))

=> r3c9 <> 39, (base digits missing in the mirrored target cell)

I am able to understand why 2,5,9 can be eliminated from cell (2,4).

But I don't understand why base candidates (3 and 9) missing in the opposite target cell (2,4) cannot be true in the mirror cell (3,9).

I've been trying to do a proof-by-contradiction but never arrive at a contradiction.

So to to be fair, the explanation should NOT USE the inferences made in parallel or unneeded assumptions of the pattern:

- Do not use that 1 must be in (2,4), so it can not be in (2,9), so (3,9) must be 1.

- Do not use that 3/9 are a locked-pair in row 5, just that there is (at least) a weak-link there.

So in my reasoning... let's say (for contradiction sake) that (3,9) is 3, then (5,7) is 3, then (5,3) is not 3.

Also because 3 is in neither target cells, then 3 is not in (1,1) or in (1,2), so (2,3) must be 3 and (1,6) must be 3.

After these types of naive eliminations there doesn't seem to be an obvious contradiction for the candidate 3s:

- Code: Select all
`+--------------+----------------+---------+`

| 159 19 2 | 149 8 3 | 59 6 7 |

| 6 7 3 | 1259 29 259 | 8 24 1 |

| 1589 189 4 | 6 7 29 | 59 24 3 |

+--------------+----------------+---------+

| 139 1349 6 | 259 2349 259 | 7 8 9 |

| 78 2 9 | 78 1 6 | 3 5 4 |

| 3789 3489 5 | 79 349 789 | 6 1 2 |

+--------------+----------------+---------+

| 239 6 1 | 2789 29 2789 | 4 37 5 |

| 239 39 8 | 247 5 2479 | 1 37 6 |

| 4 5 7 | 3 6 1 | 2 9 8 |

+--------------+----------------+---------+

Obviously, I will later see contradictions, but those are too indirect. So there must be something else I'm missing.