Task description: link
Pretty fun one. I got really tripped up by the solution for part 1 though. I was calculating the area wrong (my width and height were off by one) and the difference between my area and the actual area happened to be the same as the number of elves. So when it said "how many empty ground tiles", I was confused because it seemed to be any ground tiles, empty or not.
Now I'm trying to figure out how to optimize this. Part 2 takes 4-5 seconds to run. Hmm.