The New Sudoku Players' Forum

[Yogi]

000001023000200140000030506070805600008002000100490000034900005760000000905000400

Quad.png (11.37 KiB) Viewed 740 times

I think this came from Hoduku and it’s supposed to be solved with a Hidden Quad, but I can’t find it.
However I did find the Triple (389)r348c8 which discovered the Pairs (57)r56c8 => (28)r6c79 and solved 5r6c2, which lead on to here:
000001023000200140000730506070815604008072051150490070834900015760000000905000460
I still don’t see the Quad, though. Can you spot it?

[SpAce]

There's one in box 1:

Code: Select all

.--------------------.----------------.-----------------.
| *56-4  489  *67-9  |  56  4568  1   |  789   2    3   |
| *356   89   *367-9 |  2   568   689 |  1     4    789 |
|  24    12    129   | <7  <3     489 | <5     89  <6   |
:--------------------+----------------+-----------------:
|  23   ^7     239   |  8   1     5   |  6     39   4   |
|  346   49    8     |  36  7     2   |  39    5    1   |
|  1    ^5     36    |  4   9     36  |  28    7    28  |
:--------------------+----------------+-----------------:
|  8    ^3     4     |  9   26    67  |  27    1    5   |
|  7    ^6     12    |  15  2458  48  |  2389  389  289 |
|  9     12    5     |  13  28    378 |  4     6    278 |
'--------------------'----------------'-----------------'
Hidden Quadruple: 3,5,6,7 in r1c13,r2c13 => r1c1<>4, r12c3<>9

It's actually most easily seen without candidates, if you look at row 3 and column 2. They both have (3,5,6,7) which leaves just four cells in box 1 for those four digits.

[Yogi]

So easy, when the Head's in the right place!
Thanx