Leaderboard Positions - Part 1: 2165, Part 2: 1224
Hello all! In this puzzle, we are figuring out the price of different regions based on their area and perimeter. Because we are working with
grids, each character is considered 1 unit of area, and any edge that is not touching the same region is 1 unit of
perimeter. For example...
AAAA
BBCD
BBCC
EEEC
is parsed as
----
|AAAA|
----
--
|BB|
|BB|
--
-
|C|_
|CC|
-|C|
-
-
|D|
-
--
|EE|
--
There could also being multiple regions that have the same name. If they are not touching, then they are different regions. In part 1, we need
to count all the regions' area and perimeter, multiply them, then add it all up. To do this, we can use a recursive flood fill that returns the
area and perimeter counts as well as the squares in the regions. Then, when looping over the grid, we can keep track of all the regions and make
sure they one count once. For part 2, we need to combine perimeter edges that are next to each other. Using the example above, A will now have a
perimeter of 4 and not 10. C will have a perimeter of 8 and not 10. This requires us to
check which perimeters are next to each other and only count it once. I chose to loop over all directions, from smallest to largest, and make
perimeters 'valid' or not if they needed to be counted.