Day 3

1 files changed, 29 insertions, 0 deletions

diff --git a/2015/day3.exs b/2015/day3.exs
new file mode 100644
index 0000000..129d019
--- /dev/null
+++ b/2015/day3.exs
@@ -0,0 +1,29 @@
+contents = File.read!("inputs/day3.txt")
+directions = String.codepoints(contents)
+
+move = fn
+  "^", {x, y} -> {x, y - 1}
+  "<", {x, y} -> {x - 1, y}
+  ">", {x, y} -> {x + 1, y}
+  "v", {x, y} -> {x, y + 1}
+end
+
+coordinates = Enum.scan(directions, {0, 0}, move)
+
+unique_coordinates = Enum.uniq(coordinates)
+
+IO.puts("Unique Households for Just Santa: #{length(unique_coordinates)}")
+
+get_shared_coords = fn offset ->
+  Enum.with_index(directions)
+  |> Enum.filter(fn {_, i} -> rem(i, 2) == offset end)
+  |> Enum.map(fn {val, _} -> val end)
+  |> Enum.scan({0, 0}, move)
+end
+
+regular_santa_coordinates = get_shared_coords.(0)
+robo_santa_coordinates = get_shared_coords.(1)
+shared_coordinates = regular_santa_coordinates ++ robo_santa_coordinates
+unique_shared_coordinates = Enum.uniq(shared_coordinates)
+
+IO.puts("Unique Households for Santa and RoboSanta: #{length(unique_shared_coordinates)}")