## Sudoku - Step by Step

After we have gained knowledge about the Sudoku rules and the aids for solving a sudoku, we have to use our knowledge in praktice to solve a sudoku.

Let's start with a Step by Step tutorial to solve a sudoku. For this case we use the same sudoku wich has been used to explain the rules for sudoku and for the techniques. This sudoku is one of the easier levels.

## The first Stepp to sovle a sudoku

Let's take a look at the sudoku. You can see that the number 5 appears very often. So we scan the soduko to find out where we can place an other number 5.

Due to the situation of the 5 in our sudoku we can exclude the red marked areas for placing an other 5. So we recognize that in the lower right block has the number 5 to be placed in the green marked field.

## one more 5

After we have placed the 5 on bottom right we scan again the sudoku and now we find an other position for a 5 in the lower middle block (green marked).

An other scan shows that there now always two positions in each block where we can place a 5

## an other number - same game

To get closer to the solution of the sudoku we start a scanning with an other number. We choose number 8 beacaus this number is already placed in two of the upper blocks.

The scan shows up directly the one and only allowed position fort he 8.

The new position of the 8 in the upper left block was a possible position for a 5 too. So we have excluded a position for a 5. On how we get a profit of this we will see later. Now lets go on with the 8.

## Go ahead with the 8

With a further scan fort he 8, we can see an other position for an 8 in our sudoku.

Now a well trained sudoku eye can see at witch position in the lower left block the 9 has to be placed. Three of the remaining last four fields in the block are now excluded by the 9 in the middle left block.

But this just besides. We go ahead with the scan for an other 8.

## And another 8

An extended scan shows up the position for the 8 in the lower middle block.

Thats it with the 8. A re-examine does not show any new insights.

Then let's take a look if the excluding of the position of the 5 in step 4 will help us out now. So we start scanning for the 5.

## Higher logic for the 5

The renew scan fort he 5 shows up that there is no 5 in three blocks. But in these blocks are each 2 possible positions for the 5.

But the two positions in the upper left block are in the same row (yellow). This means, that we can exclude one position in the middle block (yellow/red striped) and we have one position for the 5.

You don't need this technique for this easier sudoku, you could solve it without tihs technique. But it could be possible at some difficulty sudokus that you need to use your logical understandings. Just that why I have implanted this technique.

And now a schon for 2 and 4 in a fast run.

## 2 and 4 scanned very quic

So all the 4 are filled in!

## Viewed column by column

Let's take a look at the blue rounded column. Whitch numers are missing?

There are missing the 1, 2, 6 and the 9. We can see that the 1 can't be placed in the upper three fields, because the 1 is already placed in this block.

Therefore the one and only position fort he 1 is in the lower block.

## And crosswise

In the residing last three fields we have to place the 2, the 6 and the 9. But we don't know exactly where.

So let's take a look at the corresponding row. You can see that there are already the 2 and the 6. Jet we know that this position is for the number 9.

There is nothing more to solve in this column at the moment.

## It works line-by-line too

Now let's take the row whitch helped us out just before to find out the position in the column for the 9. Here are just two numbers missing. The 3 and the 7.

In the column of a free field in our row is already a 3 so can there be placed only the 7.

And the last remaining free field in this row is fort he number 3.

You can use this on a block of course, too. It means to look witch number is missing in a single block.

## Everything has an end

Our introductory in sudokus is here at it's end. All the techniques and hints to solve a sudoku are used. So it will be easy for you to solve this and other sudokus completely.

Our Tipp: print the Sudokus out, take place in a cosy neat place and solve the sudokus in peace...

Have fun!