3
$\begingroup$

enter image description here

Related to this Q&A. I am looking for a pattern that could be applied in order to solve this Sudoku.

The current patterns that I apply:

  • Ensure that every digit appears once in every block
  • Ensure that there is a unique sequence from 1 to 9.

Now I am blocked as the block top right could contain a 8 and a 5, but I cannot rationalize where the 8 and where the 5 should be placed. What pattern am I missing?

As encouraged by @legorhin I tried to come up with possible solutions for the Sudoku cells.

enter image description here

Improve this question
$\endgroup$
2
  • $\begingroup$ solve other parts of the puzzle then come back to it later $\endgroup$
    – Legorhin
    Commented Oct 14, 2019 at 18:01
  • 1
    $\begingroup$ Why have you got a 7 in r7c2? What about r9c3? $\endgroup$
    – JMP
    Commented Oct 14, 2019 at 18:27

3 Answers 3

Reset to default
2
$\begingroup$

The first thing I saw was:

In the middle column, the 6 has to be on the top row, because the other two rows already contain a 6.

The second thing I saw:

The cell at R7C2 can only be a 3 because all other numbers are in a shared row/column/sector.
This makes R8C6 a 3 also, which makes R2C5 a 3. I think after that it gets easier.

Improve this answer
$\endgroup$
2
$\begingroup$

Look at the bottom middle block. The 6's in row 6 column 4 and row 7 column 8 mean that the $6$ in this block is on the right hand side. Using this with the 6 at r2c9 and the 6 at r6c4 mean that r1c5=6.

Also:

The 6's at r4c3 and r7c8 collude with the 9's at r5c3 and r7c7 to means that r8c1 and r1c9 are both 6 and 9. This means the remainder of the lower left block is {1,3,8}, and therefore r7c2=3, r7c1=1 and r8c3=8.

Improve this answer
$\endgroup$
1
  • $\begingroup$ You and I are seeing the same thing, at the same time, lol. $\endgroup$
    – JS1
    Commented Oct 14, 2019 at 18:15
2
$\begingroup$

My late contribution:

The $6$ supplied by other answers could have been solved without filling in any possibles. There are three numbers $3,6,7$ missing from the centre column, and the $6$ can only go in the top cell.

Similarly there are three numbers $3,7,9$ missing from the second column, and the $3$ can only go in the cell at the top of the bottom block (yet you marked the possibilities $3,7$).

So this is one of my techniques: for any row, column or block already well populated, see where the missing ones can fit.

Allied to this, is that when you have a duplicate pair possible in any row, column or block, as you have with the $3,7$ in the centre column, you can remove all other $3$s and $7$s in that element - here leaving that lone $6$.

The same goes in the rarer case when you spot a set of three numbers appearing as the only possibles in three cells.

Improve this answer
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.