4
$\begingroup$

I keep staring at this sudoku puzzle and can't seem to find the next move.

enter image description here

Is the next move a guessing move? I thought sudoku always has clear solutions, you just need to figure them out.

$\endgroup$
  • $\begingroup$ I think your initial numbers are already wrong.. $\endgroup$ – Jamal Senjaya Jan 16 '18 at 10:09
  • $\begingroup$ Can you be more specific? I don't think I've made a mistake. My numbers are written in blue $\endgroup$ – Adelin Jan 16 '18 at 10:11
  • 1
    $\begingroup$ It might be useful to update your image without the little hint/guess grey numbers, as they are confusing. E.g. the top right set of 9 squares has 2 squares with a little 4, and two with a little 7. Just keep the large black numbers (the starting ones) and the blue ones (your input). $\endgroup$ – Phylyp Jan 16 '18 at 11:04
  • $\begingroup$ @Adelin - thank you. I have been able to replay from the start to your current position, except for the 2/7/5 in column 1, and the 5 in column 2. Could you shed some light on how you arrived at those? R6C1 can be 2/5/7, R5C1 can be 2/5, and R7C1 and R6C2 can both be 5/7. $\endgroup$ – Phylyp Jan 16 '18 at 11:31
  • $\begingroup$ 5 is for sure in R6C1, dicatated by top middle 3x3 cell. There, you can have 8 and 3 exclusively in the R1 C4 respectively C5, which tells us that the remaining 1 and 5 are on R3, therefore telling us that the 5 in top left 3x3 cell is on C3 which, working togheter with the 5 from R8C6, cuts the bottom left 3x3 in such a way that 5 is only possible in R6C1. The remaining two (7 and 2) are easy $\endgroup$ – Adelin Jan 16 '18 at 11:42
5
$\begingroup$

No you shouldn't guess. The puzzle has a unique solution. However, you can't continue unless you calculate all possibilities. Once you do that, solving the puzzle will be easy. I have added the possibilities below. If you want to do that on your own, don't look down.

Sudoko possibilities

Once you do that, I think the next step is clear:

Next step

Note:

others pointed out in the comments that it is unclear why that particular cell cannot have a 5. To explain, in the red column there are 2 cells indicated in blue. They have two possibilities: (3,5). No matter how the possibilities are distributed, any of the cells will definitely have a 3 and the other a 5. Which makes it impossible for any other cell in that column to have a 3 or a 5. explanation

Additional explanation (requested by the OP):

Why can't there be a 7 in the last row? Because it can only be in row 7.Explained below: additional explanation

$\endgroup$
  • 2
    $\begingroup$ How is it clear that in that place it's a 7? Why is it not a 5? $\endgroup$ – Adelin Jan 16 '18 at 10:53
  • $\begingroup$ @Adelin if you look at thd possible numbers at that cell, you can see there is only a 7. What makes you think there should be a 5 $\endgroup$ – Mhmd Jan 16 '18 at 11:00
  • $\begingroup$ What makes you think there shouldn't be a 5 in that cell? Nothing around it prevents that cell from containing 5. $\endgroup$ – votbear Jan 16 '18 at 11:03
  • 1
    $\begingroup$ Let us continue this discussion in chat. $\endgroup$ – Mhmd Jan 16 '18 at 11:49
  • 1
    $\begingroup$ Ah, that clarifies it. Thanks for the explanation. $\endgroup$ – votbear Jan 17 '18 at 2:05
0
$\begingroup$

For a start:

2,4 and 7 cannot be in the middle square bottom row, which means that there has to be 1 and 6.

This, in turn, means that:

the 8 must be in the top middle and that there must be a 5 to the middle left in the middle square, and so on.

$\endgroup$
  • $\begingroup$ Welcome to Puzzling! This question already had an answer accepted 11 months ago - be sure to read other answers to make sure you aren't duplicating content. $\endgroup$ – Deusovi Dec 5 '18 at 22:51

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

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