1 files changed, 75 insertions, 0 deletions

diff --git a/day18/__init__.py b/day18/__init__.py
new file mode 100644
index 0000000..0500963
--- /dev/null
+++ b/day18/__init__.py
@@ -0,0 +1,75 @@
+# -*- coding: utf-8 -*-
+from abc import ABC
+from typing import Iterator, Set
+
+from aoc import BaseAssignment
+from aoc.datastructures import Coordinate3
+from aoc.mixins import BreathFirstSearchMixin
+
+
+class Assignment(BaseAssignment[int, Coordinate3], ABC):
+    def parse_item(self, item: str) -> Coordinate3:
+        x, y, z = item.split(",")
+        return Coordinate3(int(x), int(y), int(z))
+
+    @staticmethod
+    def open_sides(blocks: Set[Coordinate3]) -> int:
+        return len(
+            [
+                neighbour
+                for block in blocks
+                for neighbour in block.neighbours(True)
+                if neighbour not in blocks
+            ]
+        )
+
+
+class AssignmentOne(Assignment):
+    example_result = 64
+
+    def run(self, input: Iterator[Coordinate3]) -> int:
+        blocks = set(input)
+        return self.open_sides(blocks)
+
+
+class AssignmentTwo(Assignment, BreathFirstSearchMixin[Coordinate3]):
+    example_result = 58
+
+    def run(self, input: Iterator[Coordinate3]) -> int:
+        blocks = set(input)
+
+        lower_x = min([block.x for block in blocks]) - 1
+        higher_x = max([block.x for block in blocks]) + 1
+        lower_y = min([block.y for block in blocks]) - 1
+        higher_y = max([block.y for block in blocks]) + 1
+        lower_z = min([block.z for block in blocks]) - 1
+        higher_z = max([block.z for block in blocks]) + 1
+
+        all_coordinates = set(
+            Coordinate3(x, y, z)
+            for x in range(lower_x, higher_x + 1)
+            for y in range(lower_y, higher_y + 1)
+            for z in range(lower_z, higher_z + 1)
+        )
+
+        def nb(c):
+            for n in c.neighbours(True):
+                if n in all_coordinates and n not in blocks:
+                    yield n
+
+        outer_coordinates = {
+            coordinate
+            for coordinate in self.bfs(
+                Coordinate3(lower_x, lower_y, lower_z),
+                neighbours=nb,
+            )
+        }
+
+        return len(
+            [
+                neighbour
+                for block in blocks
+                for neighbour in block.neighbours(True)
+                if neighbour in outer_coordinates
+            ]
+        )