Sudoku Howto

 

Sudoku explained step by step  

Now that we know the Sudoku rules and have already familiarized ourselves with the solution techniques, we need to put both into practice in order to be able to solve a Sudoku.

Let’s take a step-by-step approach to solving a Sudoku. To do this, we will use the Sudoku that has already been used to explain the rules and techniques. This is a Sudoku of the easier difficulty level.

the first step to the Sudoku solution  

We look at the Sudoku and can see that the 5 is given quite often. So let’s scan the Sudoku and see if we can fill in another field.

Due to the position of the 5s in the Sudoku, we can exclude the red colored areas for further 5s. And so we recognize directly where a 5 must be in the lower right block (green field).

and another 5.  

After we have entered the 5 at the bottom right, we expand the scan to include the new 5 and recognize the unique position of the 5 in the lower middle block.

By extending the scan again, this time no further position of a number can be determined exactly. There are at least two positions to choose from for the 5s in the last three remaining blocks.

other number - same game  

To get closer to the solution of the Sudoku, we perform a scan with a different number. The number 8 is ideal for this, as it is already given in two of the upper blocks.

The scan of the Sudoku also immediately reveals the position of another 8.

The position of the 8 found in the top left block was also a possible position for a 5. So we were able to rule out a possible position for a 5, we’ll see how far this helps us later, first continue with the 8.

continue with the 8  

Due to the extended scan with the 8, we already recognize another position for an 8 in our Sudoku.

An experienced Sudoku eye will now also recognize where the 9 must be in the lower left block. Of the four remaining fields, 3 are excluded by the 9 in the middle left block. But we are not interested in that yet. We’ll continue our scan with the 8 first.

and another 8  

An extended scan shows us the position of the 8 in the bottom center block.

And that’s it for the 8. A new scan does not provide any new information.

Let’s see if the previous exclusion of the one possible 5 position helps us and scan again with the 5.

higher logic around the 5  

The new scan with the 5 shows us that there are still 2 possible positions in each of the three blocks that do not yet contain a 5.

But the two possible positions of the 5 in the top left block (yellow) are on the same line. This means that one possible position for the 5 in the top middle block can be excluded in any case (yellow/red stripes) and therefore only one possible position remains there.

For this simpler Sudoku it is not really necessary to use this technique, you could also solve it this way. But for more difficult Sudokus, it may well be that this is the only way to find a solution. I have therefore briefly incorporated this technique here.

And now a quick scan of 2 and 4.

2 and 4 scanned very quickly  

viewed column by column  

Now let’s take the column with the blue border and see which numbers are still missing.

1, 2, 6 and the 9 are still missing. We also notice that the 1 cannot be in the three upper fields as it is already contained in the upper right block.

This leaves only the field in the bottom block for the 1.

and across  

In the 3 remaining fields of this column, we still have to enter 2, 6 and the 9, but we don’t know exactly where.

So we take a look at the corresponding rows and realize that one row already contains the 2 and the 6, so we already know the position of the 9 in our column.

That’s all we can solve in this column at the moment.

also works row by row  

Then let’s look at the row that just helped us to determine the position of the 9 in the column, because only two numbers are missing here, 3 and 7.

The column of the one free field already contains a 3, so the 7 must be there.

And the last remaining field in this row can then only contain the 3.

Of course, you can also apply this to a block, i.e. look at which numbers are still missing and where they can be placed.

everything has an end  

Our introduction to Sudoku is now over, the techniques required to solve a Sudoku have all been applied. And so it is now easy to solve this and other Sudoku puzzles completely, even if a Sudoku online is solved.

Our tip:  

Sudoku to print out and sit down in a cozy place and puzzle in peace and quiet…

Have fun!

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 Sudoku explained step by step  
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