8

Start with a square. Any side of the square can be either straight or have an interlocking pattern, as shown in the two examples below:

enter image description here

That gives $2 \times 2 \times 2 \times 2 = 16$ possible squares.

Is it possible to create a $4 \times 4$ jigsaw puzzle (outside borders straight) with these $16$ pieces? Rotation or flipping of pieces is not allowed.

Jens
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2 Answers2

10

Here is an alternative solution that has a bit more structure to it:

+---+---+---+---+
|   %   %   |   |
+-%-+-%-+-%-+-%-+
|   %   %   |   |
+-%-+-%-+-%-+-%-+
|   %   %   |   |
+---+---+---+---+
|   %   %   |   |
+---+---+---+---+

Looking at the 5 horizontal lines, there are 4 adjacent pairs, and each combination occurs exactly once. The same goes for the vertical lines. Therefore all the tiles are different, and every combination of four sides occurs exactly once.
Jaap Scherphuis
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8

I think this has them all:

+---+---+---+---+
| 2 % 3 % 2 | 1 |
+-%-+-%-+-%-+-%-+
| 3 % 4 % 3 % 3 |
+-%-+-%-+---+-%-+
| 2 % 2 | 0 | 2 |
+---+---+---+-%-+
| 1 % 2 % 1 | 1 |
+---+---+---+---+

I went with % for the interlocking pattern sides, and the number is how many of those sides a given square has.

hagfy
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