Time Limit: 2 Seconds
Memory Limit: 65536 KB
Consider the following 5 picture frames placed on an 9 x 8 array.
Now place them on top of one another starting with 1 at the bottom
and ending up with 5 on top. If any part of a frame covers another it hides
that part of the frame below.
Viewing the stack of 5 frames we see the following.
In what order are the frames stacked from bottom to top? The answer
Your problem is to determine the order in which the frames are stacked from
bottom to top given a picture of the stacked frames. Here are the rules:
1. The width of the frame is always exactly 1 character and the sides are never
shorter than 3 characters.
2. It is possible to see at least one part of each of the four sides of a frame.
A corner shows two sides.
3. The frames will be lettered with capital letters, and no two frames will
be assigned the same letter.
Each input block contains the height, h (h<=30) on the first line and the
width w (w<=30) on the second. A picture of the stacked frames is then given
as h strings with w characters each.
Your input may contain multiple blocks of the format described
above, without any blank lines in between. All blocks in the input must be processed
Write the solution to the standard output. Give the letters of the frames in
the order they were stacked from bottom to top. If there are multiple possibilities
for an ordering, list all such possibilities in alphabetical order, each one
on a separate line. There will always be at least one legal ordering for each
input block. List the output for all blocks in the input sequentially, without
any blank lines (not even between blocks).
Source: South Africa 2001