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Mini Sudoku

Tri2000
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Mini Sudoku

#439842

Postby Tri2000 » September 5th, 2021, 4:17 pm

This is a bit of a long shot, but does anyone have the answer to the Daily Telegraph Mini Sudoku puzzle #3386 which was published Thursday 2 Sep and the answer should have been in the Friday paper (which I don't have)

I am convinced there is a mistake and it is unsolvable, but that would be unlike a national newspaper to make such an error, surely? :shock:

Mini Sudoku is a 6 x 6 grid where numbers in rows and columns must have 1 - 6, and also within each block of 6, the shaded cells have no special meaning.

Image

Itsallaguess
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Re: Mini Sudoku

#439845

Postby Itsallaguess » September 5th, 2021, 4:36 pm

Tri2000 wrote:
I am convinced there is a mistake and it is unsolvable, but that would be unlike a national newspaper to make such an error, surely?


There's no mistake...

I didn't want to embed the answer as a picture, just in case you want to have another go knowing it's OK, but if you want to see the answer then here's a picture link -

https://i.imgur.com/2MLdb8V.png

Cheers,

Itsallaguess

Watis
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Re: Mini Sudoku

#439851

Postby Watis » September 5th, 2021, 5:04 pm

I solved it, as per the answer from Itsallaguess, after getting bogged down early on.

Here's a clue, in case it helps:

SPOILER ALERT:










































Treat the top left to bottom right diagonal as needing to meet the 1-6 rule.

(The other diagonal does not meet the rule.)

HTH,

Watis

Tri2000
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Re: Mini Sudoku

#439856

Postby Tri2000 » September 5th, 2021, 5:31 pm

Thanks. I tried it again and managed to solve it with some trial and error.

It was certainly one of the more tricky 6x6's I have seen and only labelled as "Moderate" difficulty. I think that actually threw me a bit as I wasn't expecting a medium level puzzle to require that.

I only see the paper if my good lady picks up a few things from Waitrose and grabs a free copy, hence the disaster of failing to complete it when I started it yesterday!

UncleEbenezer
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Re: Mini Sudoku

#439895

Postby UncleEbenezer » September 5th, 2021, 9:06 pm

"It's impossible" is a mental block condition.

Funnily enough, I solved your puzzle fairly easily. I didn't post 'cos someone already had. Then I went to do a regular online sudoku, and found myself in a similar mental block as I came to an impossible situation not once (as happens occasionally) but twice, without ever making a move I was uncertain of. Third time lucky I caught what I'd been missing, but if I hadn't just read this I'd probably have left it for tomorrow!

Gengulphus
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Re: Mini Sudoku

#439932

Postby Gengulphus » September 6th, 2021, 7:36 am

Tri2000 wrote:Thanks. I tried it again and managed to solve it with some trial and error.

It was certainly one of the more tricky 6x6's I have seen and only labelled as "Moderate" difficulty. I think that actually threw me a bit as I wasn't expecting a medium level puzzle to require that.

It doesn't seem to me to require trial&error, so I'd guess you're missing one or more of the trial&error-free steps that are available. To help you identify at least one of them, here's a trial&error-free spoiler...

1) The 6 in the last column must be in the 6th row, as all other cells in that column are either already occupied or already have a 6 on the same row.
2) All the remaining 5s can now be located by looking for them in the bottom-right corner block and the left central block (in either order), then the top-left and top-right corner blocks (also in either order).
3) The 4 in the bottom-right corner block cannot be in its middle column, so must be in one of its top-left and top-right corner cells. So in the 2nd column, the two remaining blank cells must be filled with a 4 in the 3rd row and a 1 in the 5th row, not the other way around.
4) That allows us to locate the 4 in the right central block and the 1 in the bottom-right corner block.
5) Those in turn allow us to locate the 4 in the bottom-right corner block and the 1 in the left central block.
6) All the remaining 2s can now be located by looking for them in the left central block, then the top-left corner block and the right central block (in either order), then the bottom-right corner block.
7) All the remaining 3s can now similarly be located by similar block-by-block considerations.
8) All the remaining 1s, 4s and 6s can now be located similarly - tackle them in any order.

Gengulphus

modellingman
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Re: Mini Sudoku

#440101

Postby modellingman » September 6th, 2021, 4:42 pm

I agree with Gengulphus, trial and error is not necessary.

Without looking at any spoilers so far...


Columns 2 and 6 provide a starting point. In column 2, the only possible location of the 5 is in row 2. In column 6, the pair of possibilities {3,4} must occupy rows 3 and 5, so these possibilities can be eliminated from rows 1 and 6, leaving solutions of 5 in row 1 and 6 in row 6.

The two remaining 5's can now be added to the mid-left and bottom-right blocks in cells (4,3) and (6,4) using a (row, column) convention.

In row 6, the 4 cannot be in column 5, so must be in either column 1 or column 3. However, in the bottom-left block, cell (5,2) has only possibilities of {1,4} so the 4 can be eliminated leaving a solution of 1 in cell (5,2), with consequential solutions of 1 in cell (6, 5) and 4 in cell (3,2).

The missing 3 and 4 can now be added to column 6 in cells (3,6) and (5,6) respectively, whilst the missing 1 and 2 can be added to the mid-left block in cells (3,3) and (4,1), respectively, allowing row 3 to be completed with a 2 in cell (3,4).

Completion of rows 4 and 5 follow easily with a 4 in cell(4,4), a 6 in cell (4,5), a 3 in (5,4) and a 2 in (5,5), allowing column 5 to be completed with a 5 in cell (2,5) and then column 4 to be completed with 1 in cell (1,4) and a 6 in (2,4).

The 1 in the top-left block can only be placed in cell (2,1), leaving row 2 to be completed with a 4 in cell (4,3) and the block is completed with a 3 in cell(1,1) and a 2 in (1,3). This leaves two remaining unsolved cells of (6,1) and (6,3) which are trivially solved as 4 and 3, respectively.

doolally
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Re: Mini Sudoku

#440105

Postby doolally » September 6th, 2021, 4:53 pm

I'm intrigued by the shaded cells. I've not done a sudoku for a while (I used to do them daily), but I don't recollect ever seeing shaded cells.

Why are they there at all?

doolally

modellingman
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Re: Mini Sudoku

#440119

Postby modellingman » September 6th, 2021, 5:32 pm

Now with correction...



Columns 2 and 6 provide a starting point. In column 2, the only possible location of the 5 is in row 2. In column 6, the pair of possibilities {3,4} must occupy rows 3 and 5, so these possibilities can be eliminated from rows 1 and 6, leaving solutions of 5 in row 1 and 6 in row 6.

The two remaining 5's can now be added to the mid-left and bottom-right blocks in cells (4,3) and (6,4) using a (row, column) convention.

In row 6, the 4 cannot be in column 5, so must be in either column 1 or column 3. However, in the bottom-left block, cell (5,2) has only possibilities of {1,4} so the 4 can be eliminated leaving a solution of 1 in cell (5,2), with consequential solutions of 1 in cell (6, 5) and 4 in cell (3,2).

The missing 3 and 4 can now be added to column 6 in cells (3,6) and (5,6) respectively, whilst the missing 1 and 2 can be added to the mid-left block in cells (3,3) and (4,1), respectively, allowing row 3 to be completed with a 2 in cell (3,4).

Completion of rows 4 and 5 follow easily with a 4 in cell(4,4), a 6 in cell (4,5), a 3 in (5,4) and a 2 in (5,5), allowing column 5 to be completed with a (CORRECTION) 3 in cell (2,5) and then column 4 to be completed with 1 in cell (1,4) and a 6 in (2,4).

The 1 in the top-left block can only be placed in cell (2,1), leaving row 2 to be completed with a 4 in cell (4,3) and the block is completed with a 3 in cell(1,1) and a 2 in (1,3). This leaves two remaining unsolved cells of (6,1) and (6,3) which are trivially solved as 4 and 3, respectively.


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