9
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A light jigsaw puzzle.

Start with a square. Assume two adjacent sides (top and left) are always straight and the other two adjacent sides (bottom and right) can be either straight, convex or concave. That gives $3 \times 3 = 9$ possible squares. Below we see $3$ example squares where the bottom is straight.

enter image description here

Is it possible to create a $3 \times 3$ jigsaw puzzle (outside borders straight) with these $9$ pieces? Rotation of pieces is allowed, but flipping of pieces is not.

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18
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I think

this does it:

+---+---+---+
|   >   |   |
+-v-+-v-+---+
|   >   |   |
+---+---+-^-+
|   >   |   |
+---+---+---+

having the correct inventory of: one with two lumps, one with two dips, two with one of each (in the two different orientations), two with one lump, two with one dip, one with none.

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17
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Here's one possible solution:

 ------- ------- -------
|       |       |       |
|       |       C       |
|       |       |       |
 ------- ------- -------
|       |       |       |
|       |       C       |
|       |       |       |
 ---U--- ---U--- ---U---
|       |       |       |
|       |       C       |
|       |       |       |
 ------- ------- ------- 

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  • $\begingroup$ I beat you by one second :-). $\endgroup$ – Gareth McCaughan Feb 24 at 1:35
  • $\begingroup$ @GarethMcCaughan May I ask how you got the spoiler to work with the code? $\endgroup$ – tobiashellbusch Feb 24 at 1:50
  • 1
    $\begingroup$ By using <pre>...</pre> at start and end, and putting >! at the start of each line. $\endgroup$ – Gareth McCaughan Feb 24 at 1:59
  • 2
    $\begingroup$ @user3574641; if you want to know how something is done, there is a 'edit' button at the base of each post - click it and you can see the post's source text. $\endgroup$ – JMP Feb 25 at 6:33
  • $\begingroup$ Thanks a lot, I didn't realize that was possible on other people's posts. $\endgroup$ – tobiashellbusch Feb 25 at 17:07
5
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A different structure:

 +---+---+---+
 |   >   |   |
 +-v-+-v-+---+
 |   |   >   |
 +---+---+-^-+
 |   >   |   |
 +---+---+---+

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