- Code: Select all
`*--------------------------------------------------------------*`

| 6 4 8 | 359 139 13 | 2 35 7 |

| 2 7 35 | 8 4 6 | 9 135 13 |

| 1 9 35 | 35 2 7 | 4 6 8 |

|--------------------+--------------------+--------------------|

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

| 9 5 b26 |c36 7 8 | 13 4 123 |

| 7 26 1 | 4 36 9 | 5 8 23 |

|--------------------+--------------------+--------------------|

| 5 8 9 | 2 136 134 | 7 13 46 |

| 34 126 a26 | 7 8 5 | 13 9 46 |

| 34 1-6 7 |d369 1369 134 | 8 2 5 |

*--------------------------------------------------------------*

In more conventional Sudoku terminology what bat was describing is a Skyscraper.

Look at the cells marked abcd.

If cell a (Row 8 Column 3 or r8c3 for short) is not 6 then r5c3 (cell b) must be 6 (only 2 6's in Column 3).

So r5c4 (cell c) is not 6. So r9c4 must be 6 (only 2 6's in Column 4).

You can reverse this logic and start by assuming r9c4 is not 6 and conclude that r8c3 is 6.

The result of all this is that at least one of r8c3 and r9c4 must be 6. They could both be 6 but they can't both be not 6.

Since r9c2 can see both cells a and d you can remove the 6 from there. That solves that cell and the puzzle solves easily after that.

Here's link to a site that discusses Skyscrapers (and a lot of other solving techniques).

http://hodoku.sourceforge.net/en/techniques.phpLeren