The New Sudoku Players' Forum

[Hud]

They put one in that Pappocom didn't like. I tried it and possibly found the key but was it just luck?
It was another of my meager attempts at swordfishing.
Here's the beginning grid and what I arrived at after basic moves.
I also tried to bolden the swordfish candidates and underlined the candidate that I removed which solved the puzzle.

OK, I'm afraid the bold and underline didn't work so my swordfish on 9's was columns 2, 3, and 5.
I eliminated the 9 at r6c1 and the puzzle fell apart after that.
If I was wrong, I'm used to it. The puzzle did solve though.

Code: Select all

+-------+-------+-------+
| 1 6 . | . . 2 | . . 5 |
| . . . | 4 6 9 | . . . |
| . . 7 | . 8 . | 3 6 . |
+-------+-------+-------+
| 8 . . | . . . | . 5 . |
| . . 3 | 2 . 4 | 9 . . |
| . 4 . | . . . | . . 3 |
+-------+-------+-------+
| . 7 1 | . 4 . | 6 . . |
| . . . | 9 2 1 | . . . |
| 2 . . | 7 . . | . 4 1 |
+-------+-------+-------+

Code: Select all

+--------------+-----------+-------------+
| 1  6    48   | 3  7   2  | 48   9  5   |
| 35 2358 258  | 4  6   9  | 1278 17 278 |
| 49 29   7    | 1  8   5  | 3    6  24  |
+--------------+-----------+-------------+
| 8  129  29   | 6  139 37 | 1247 5  247 |
| 7  15   3    | 2  15  4  | 9    8  6   |
| 69 4    2569 | 58 159 78 | 127  17 3   |
+--------------+-----------+-------------+
| 35 7    1    | 58 4   38 | 6    2  9   |
| 46 58   46   | 9  2   1  | 578  3  78  |
| 2  3589 589  | 7  35  6  | 58   4  1   |
+--------------+-----------+-------------+

[tarek]

The 9s fall into 4 rows, that is not a swordfish.

This puzzle required advanced techniques to solve, this is more like a DIABOLICAL difficulty.

[MCC]

Although the 9's don't form a swordfish they do form a jellyfish. Not that it helps in moving the puzzle on.

[CathyW]

Interestingly, there are also jelly fish on 2s, 3s, 4s and 7s, but it still doesn't help to solve the puzzle!

[Carcul]

Here is a possible solution (from the second grid above):

1. [r8c9]=8=[r2c9]-8-[r1c7]-4-[r1c3]=4=[r3c1]=9=[r6c1](-9-[r4c2])-9-[r4c3]-2-[r4c2]-1-[r5c2]-5-[r8c2]-8-[r8c9],

a continuous nice loop that enables the following eliminations:

r2c7<>8
r6c3<>9
r4c7<>2
r4c9<>2
r2c2<>5
r9c2<>5
r8c7<>8.

2. [r4c7]=4=[r4c9]-4-[r3c9]=4=[r3c1]=9=[r6c1](-9-[r4c2])-9-[r4c3]-2-[r4c2]-1-[r4c7],

a discontinuous nice loop which implies r4c7<>1. And finally:

3. [r4c3]-9-[r6c1]-6-[r6c3]-5-[r9c3]-9-[r4c3],

a XY-Wing, which implies r4c3<>9 => r4c3=2 and that solve the puzzle.

Carcul