1 files changed, 79 insertions, 0 deletions

diff --git a/day9/__init__.py b/day9/__init__.py
new file mode 100644
index 0000000..696a6dc
--- /dev/null
+++ b/day9/__init__.py
@@ -0,0 +1,79 @@
+from abc import ABC
+from collections import Counter
+from copy import copy
+from functools import reduce
+from operator import mul
+from typing import List, Tuple, Dict, FrozenSet, Iterator, Set, Callable
+
+from aoc import BaseAssignment
+
+Coordinate = Tuple[int, int]
+Field = List[List[int]]
+
+
+class Assignment(BaseAssignment, ABC):
+    def parse_item(self, item: str) -> List[int]:
+        return [int(i) for i in item]
+
+    def read_input(self, example = False) -> Field:
+        return list(super().read_input(example))
+
+    @classmethod
+    def neighbours(cls, field: Field, x: int, y: int) -> Iterator[Coordinate]:
+        for ny in list(range(max(0, y - 1), min(len(field) - 1, y + 1) + 1)):
+            if ny == y:
+                continue
+            yield (x, ny)
+
+        for nx in list(range(max(0, x - 1), min(len(field[0]) - 1, x + 1) + 1)):
+            if nx == x:
+                continue
+            yield (nx, y)
+
+    @classmethod
+    def lowest_points(cls, field: Field) -> Iterator[Coordinate]:
+        for y, row in enumerate(field):
+            for x, item in enumerate(row):
+                if all(field[ny][nx] > item for nx, ny in cls.neighbours(field, x, y)):
+                    yield x, y
+
+
+class AssignmentOne(Assignment):
+    example_result = 15
+
+    def run(self, input: Field) -> int:
+        lows = list(input[y][x] for x, y in self.lowest_points(input))
+        return sum(lows) + len(lows)
+
+
+def flatten(l: List[Set[Coordinate]]) -> List:
+    flat_list = []
+    for _ in l:
+        flat_list += _
+
+    return flat_list
+
+
+class AssignmentTwo(Assignment):
+    example_result = 1134
+
+    @classmethod
+    def find_basin_members(cls, field: Field, x: int, y: int) -> Set[Coordinate]:
+        return {
+            (x, y),
+            *flatten([
+                cls.find_basin_members(field, nx, ny)
+                for nx, ny in cls.neighbours(field, x, y)
+                if field[y][x] < field[ny][nx] < 9
+            ])
+        }
+
+    def run(self, input: Field) -> int:
+        return reduce(
+            mul,
+            sorted([
+                len(self.find_basin_members(input, x, y))
+                for x, y in self.lowest_points(input)
+            ], reverse=True)[:3],
+            1
+        )