# ConstructionProblem4/ Solution

**Terminology of notation**: the 4x4 board has 4 partial boards **A, B, C, D** which are arranged clockwise, starting in north-west like this:

## AB

## DC

Tderz: I give the 4 different orientation of the partial boards:

For easier copying the board is: (*in editing mode it looks ok*) ^{[9]}

X O
. X

Tderz

### Solution 1:

could be annotated like this

3-4

2-1

### Solution 2:

turning all +90° => forbidden position, but
+180° creates

which has m-symmetry because all symmetrically arranged subboards have too:
notation must be (and is):

1-2

4-3

[9]: copying for editing seems to make no sense here

ferdi: I certainly don't know what this is all about, but it helped you to find the solution ;-)

Tderz: Ferdi, I only wrote down the notation , because I thought that there would be many solutions, and wanted to streamline and classify the flux of incoming duplicates.
Now I think that there won't be more than those with a 4-block in the center, because of the legality problem.

Thanks for the problem!

Tderz: Speaking of a 4-block in the center ...

### Nascent solution 3 exists only temporarily :-):

2-3

1-4

Shortly after adding the 4th partial board,
the 4 stones must be captured.

therewith (illegal) solution 3 is different to other "*solution *" implying suicide.