Anyone interested in starting a Sudoko Help/Advice thread?

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duckDecoy

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#284084 30-Mar-2021 14:42

I'm not sure if anyone will find this interesting or helpful. Lets see.

I have only recently been getting into Sudoko's and wondered if anyone else would like to participate in a thread where people can ask for help with their Sudoko's and perhaps offer tips and advice in general

Quite often I get stuck and cannot figure out the next moves. There's probably a known method to get moving again (like x-wing, or swordfish etc) and if someone could both point out the solution and explain why or what technique was used then I would get much better at them. Or maybe I have missed a tick mark or got one wrong. As it stands I hit a brick wall and tend to just have to abandon it.

Attached is my latest that I am stuck on. Advice appreciated.

1 | 2 | 3

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#2684111 30-Mar-2021 15:37

For starters, in the circle is the only "3" for that square.

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duckDecoy

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#2684157 30-Mar-2021 15:48

kiwifidget:

For starters, in the circle is the only "3" for that square.

Thank kiwifidget, that was all it took to clear the board.

Feeling a little foolish about that one actually.

RunningMan

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#2684158 30-Mar-2021 15:50

kiwifidget:

For starters, in the circle is the only "3" for that square.

Pretty sure that's because there is a 3 missing from the very top right corner - it can also go there, so isn't the only 3 for the box.

kiwifidget

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#2684167 30-Mar-2021 15:57

@runningman , no, across the top is a triple 1,3,6 , thereby removing all other 3's from the top row.

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frankv

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#2684186 30-Mar-2021 16:33

kiwifidget:

For starters, in the circle is the only "3" for that square.

My approach is to go through 3 columns at a time, checking each digit. Then 3 rows at a time, checking each digit. Looking at the top-right square, 3 can only go in one of the right-hand column squares. That means you can wipe out the 3s in the right-hand column of the mid-right square.

Having 2 cells in a row, column, or square with the same 2 possible values means you can eliminate those values from the rest of that row, column, or square.

Likewise if you have 3 cells with a total of 3 possibles (they don't have to all have the same set of possible values). So, looking at the top row, at first sight the rightmost cell could also be a 1, 3, or 6. But because you already have a (1,6), (1,3,6), and (1,3) in the row, you were correct to eliminate 1,3, and 6 as possible values. So @kiwifidget is correct... the bottom-right of that square must be a 3. In which case, eliminate the other 3 from row 3 and you have a pair of (1,9)s, so eliminate 1 & 9 from the other cells in the row. That should leave you with

5,(1,9),6,8,(1,9),4,2,7,3

for that row.

I often find that when I'm stuck, there is one key cell... when I get that, all the rest solves quickly.

Also, don't try to rescue a failed sudoku... it's almost impossible to work backwards to find where the mistake is.

kiwifidget

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#2684192 30-Mar-2021 16:35

There is no "undo" in Sudoku.

There is only "start again".

😀

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ANglEAUT

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#2684265 30-Mar-2021 19:14

kiwifidget:

runningman , no, across the top is a triple 1,3,6 , thereby removing all other 3's from the top row.

Please explain the bold portion

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floydbloke

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#2684278 30-Mar-2021 19:37

ANglEAUT:

kiwifidget:

runningman , no, across the top is a triple 1,3,6 , thereby removing all other 3's from the top row.

Please explain the bold portion

Those 3 digits can only ever go in columns 1,4 or 5 in the top row. E.g. if column 1 turns out to be a 1, that forces a 6 into column 4 and 3 into column 5. Numbers 4,5,7 and 9 are already used. That leaves only 2 and 8 as possible candidates in columns 3 and 9.

I'm a fan of the NY Times online 'hard' sudoku. Usually crack it in about 20-25 minutes, best is just over 11.

I also really like sudoko variation as seen on Cracking The Cryptic . Thermo Sudoku is my favourite. There are some good videos amongst that lot, mostly older ones that can help you learn sudoku techniques (look for classic sudoku).

@duckDecoy , I'm personally not a fan of pencil-marking all possibles. I'll start with 'no more than two of ' and pairs in square regions, then in rows or columns. Then look for triples and 'naked singles'. A naked single is a cell that through a combination of the square, row and column that it 'can see' leaves just the 1 possible number.

Sometimes I use big words I don't always fully understand in an effort to make myself sound more photosynthesis.

kiwifidget

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#2684281 30-Mar-2021 19:41

what he ^^^^^ said.

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kiwifidget

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#2684291 30-Mar-2021 20:06

http://www.dailysudoku.com/sudoku/today.shtml

This is how I start each day. I really enjoy the Squigglies too.

On the first of each month the website fails to generate new puzzles, but it normally comes right by the 2nd.

There are HEAPS of archived puzzles for those days.

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floydbloke

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#2684300 30-Mar-2021 20:18

floydbloke:

...s and 'naked singles'. A naked single is a cell that through a combination of the square, row and column that it 'can see' leaves just the 1 possible number.

Next step in this one would be to find the naked single. Virtual chocolate fish to whoever spots it.