## Sudoku

Advanced methods and approaches for solving Sudoku puzzles

### Sudoku

I frequently come to a stalemate when doing the Sunday Times Superior Sudoku. There appears to be no other option than guesswork. Can anyone help.
Bump

Posts: 1
Joined: 21 April 2006

If you can post a particular puzzle, as an example, it would be easier to help.

Luna
lunababy_moonchild

Posts: 659
Joined: 23 March 2005

you should be able to solve it using just logic.
Chessmaster

Posts: 191
Joined: 21 December 2005

### Re: Sudoku

Bump wrote:I frequently come to a stalemate when doing the Sunday Times Superior Sudoku. There appears to be no other option than guesswork. Can anyone help.

A "Superior" Sudoku can have (mandatory) Triples, Quads and X-Wings in its solution, but I've never seen one with anything more complex than that.
chrisr

Posts: 11
Joined: 19 October 2005

### Re: Sudoku

chrisr wrote:A "Superior" Sudoku can have (mandatory) ...., Quads

No it doesn't, no quads allowed in a Superior (The ones compiled by Poppacom).........

Check the SUPERIOR thread in the General Forum for a DIP....

tarek

tarek

Posts: 2650
Joined: 05 January 2006

### Re: Sudoku

chrisr wrote:A "Superior" Sudoku can have (mandatory) ...., Quads

tarek wrote:No it doesn't, no quads allowed in a Superior (The ones compiled by Poppacom).........

Ah, I see. My solver program only looks for hidden pairs, triplets, quads, quintuplets etc, so presumably every hidden quadruplet I've seen has been complemented by something no worse than a naked triplet.
chrisr

Posts: 11
Joined: 19 October 2005

I myself would consider naked subsets, much easier to spot than hidden ones,...........

I have several examples of naked doubles with Hidden quad counterparts......

Spotting the hidden quad is extremely difficult.........& for it to be a genuine Hiddden quad it must have at least a naked quintuple counterpart...

tarek

tarek

Posts: 2650
Joined: 05 January 2006

tarek wrote:I myself would consider naked subsets, much easier to spot than hidden ones,....

That's because you stare at the pencilmarks, I find hidden subsets much easier to spot in a non-pmgrid.

RW
RW
2010 Supporter

Posts: 1000
Joined: 16 March 2006

### re: "quad" in Pappocom's puzzles

tarek wrote:
chrisr wrote:A "Superior" SuDoku [ a Pappocom-generated Very Hard ]
can have Triples, Quads and X-Wings

No it doesn't,
no quads allowed in a "Superior" (the ones generated by Pappocom).

i've never seen a Pappocom puzzle which needs a "quad"
- but i've never seen Pappocom stating anything on this matter.

Pat

Posts: 3551
Joined: 18 July 2005

RW wrote:That's because you stare at the pencilmarks, I find hidden subsets much easier to spot in a non-pmgrid.

On a non pm grid, both are invisible to me .

Because of what you mentioned & what Pat mentioned in the Superior thread...........

I've revised the scoring of superior to accommodate both parties.......

Would it be possible RW or Pat to rank subsets according to difficulty of spotting them from your point of view (ex would a hidden triple be easier than a naked double?)

tarek

tarek

Posts: 2650
Joined: 05 January 2006

tarek wrote:I myself would consider naked subsets, much easier to spot than hidden ones,....

RW wrote:That's because you stare at the pencilmarks, I find hidden subsets much easier to spot in a non-pmgrid.

I did indeed start solving sudokus without pencil marks, back in those days when I had a lot of time to spend on such things. This led me to discover hidden subsets long before I discovered their naked counterparts, and my solver program reflects this .
chrisr

Posts: 11
Joined: 19 October 2005

### re: subsets

tarek wrote:Would it be possible to rank subsets according to difficulty of spotting them from your point of view?
(e.g. would a hidden triple be easier than a naked double?)

for any size of a subset, i tend to see the "hidden" subset before the "naked" — but other solvers often state the "naked" is easier ( because they make a full list of the possible digits for each cell ) — so i suppose the only fair way to rank them would be to ignore the distinction between "naked" and "hidden" subsets.

when the sizes differ, i might find the "hidden" trio before its matching "naked" duo; but i consider the size important — in explaining the solution, i would certainly describe the duo rather than the trio.

Pat

Posts: 3551
Joined: 18 July 2005

### re(2): "quad" in Pappocom's puzzles

tarek wrote:
chrisr wrote:A "Superior" SuDoku [ a Pappocom-generated Very Hard ]
can have Triples, Quads and X-Wings

No it doesn't,
no quads allowed in a "Superior" (the ones generated by Pappocom).

i've never seen a Pappocom puzzle which needs a "quad"
- but i've never seen Pappocom stating anything on this matter.

or let me put it this way:
the following puzzle requires a "quad"
and is accepted by the Pappocom software within the Very Hard rating!

Code: Select all
` . . . | 1 . . | . . .  . . 2 | . . 5 | 4 . .  5 . . | . 4 . | 8 3 . -------+-------+------ 1 . 5 | 9 . 2 | . . .  4 . . | . . . | . . 8  . . . | 8 . 4 | 3 . 5 -------+-------+------ . 5 3 | . 9 . | . . 6  . . 7 | 5 . . | 1 . .  . . . | . . 6 | . . . `

~ Pat

Pat

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Joined: 18 July 2005

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