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Is this solvable without guessing or doing multiple moves in your head?

Jimmyb wrote:Is this solvable without guessing or doing multiple moves in your head?

Yes. Several simple patterns can be found which solve the puzzle. Here's one:

Code: Select all

....4..7.72..65..1.86............4....5.3...6....1..8.94...87..17....3.4.........
.------------.--------------------.---------------.
| 5  19  19  | a(2)8     4    3   | 6    7   b28  |
| 7  2   4   |   89      6    5   | 89   3    1   |
| 3  8   6   |   7       9-2  1   | 259  4    259 |
:------------+--------------------+---------------:
| 2  36  179 |   569     8    69  | 4    159  37  |
| 8  19  5   |   4       3    7   | 129  129  6   |
| 4  36  79  |   2569    1    269 | 59   8    37  |
:------------+--------------------+---------------:
| 9  4   3   |   1     d(2)5   8  | 7    6   c25  |
| 1  7   8   |   69-2    259  269 | 3    25   4   |
| 6  5   2   |   3       7    4   | 189  19   89  |
'------------'--------------------'---------------'


Skyscraper: (2)r1c4 = r1c9 - r7c9 = (2)r7c5 => -2 r3c5,r8c4; stte

In other words, the short chain proves that either r1c4 or r7c5 must be 2. Therefore 2 can be eliminated as a candidate from any cell that can see both. That leaves 9 as the only possibility for r3c5, after which the puzzle can be solved with singles.