Strips Puzzle – Answer: R2D2 – By Kenny Young

 

The 40 strips provided need to be placed into the 20x20 grid. No help has been given as to which strips are horizontal and which are vertical. As such, it is possible to build either the image below or its reflected version. Either one is clearly identifiable as R2D2.

 

	2	6	14	31	37	3	12	22	20	9	7	35	36	30	40	39	33	15	18	1
8
4
10
21
23
25
34
32
27
29
24
11
16
19
26
17
13
38
5
28

 

This one was very difficult to solve.

 

The easiest way is to note that there are 7 strips that begin with a black square. Since we do not know which of these strips are horizontal and which are vertical, the best we can say is that the top strip and the left strip together must have 7 black squares.

 

 

 

 

 

 

 

 

Likewise, there are 8 strips that end with a black square, and the bottom strip and the right strip together must have 8 black squares. Note that the black square in the bottom right appears on both the bottom and right strips.

 

 

 

 

 

 

 

 

 

There are only so many arrangements of four strips that produce 7 black squares in the top/left and 8 black squares in the bottom/right, while keeping the colors at all four corners consistent; even fewer produce the 5 blackàwhite and 6 whiteàblack transitions described in the strips. Once the outside is determined, the interior follows suit but is much less combinatorically challenging.

 

Here is a link to some truly elegant code that a player used to solve this puzzle.