From ef6e30cb6c415d23fdc89579bc468da50b1b5a12 Mon Sep 17 00:00:00 2001
From: Bruno BELANYI <bruno@belanyi.fr>
Date: Thu, 17 Dec 2020 08:55:37 +0100
Subject: [PATCH] 2020: d17: ex1: add solution

---
 2020/d17/ex1/ex1.py | 66 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100755 2020/d17/ex1/ex1.py

diff --git a/2020/d17/ex1/ex1.py b/2020/d17/ex1/ex1.py
new file mode 100755
index 0000000..dd9efee
--- /dev/null
+++ b/2020/d17/ex1/ex1.py
@@ -0,0 +1,66 @@
+#!/usr/bin/env python
+
+import itertools
+import sys
+from typing import Iterator, Set, Tuple
+
+Point = Tuple[int, int, int]
+Grid = Set[Point]
+
+
+def update(grid: Grid) -> Grid:
+    def neightbours(p: Point) -> Iterator[Point]:
+        for dx, dy, dz in itertools.product(range(-1, 2), repeat=3):
+            if dx == 0 and dy == 0 and dz == 0:
+                continue
+            yield p[0] + dx, p[1] + dy, p[2] + dz
+
+    def count_neighbours(p: Point) -> int:
+        return sum(n in grid for n in neightbours(p))
+
+    new_grid: Grid = set()
+    seen: Set[Point] = set()
+    for p in grid:
+        for n in itertools.chain(neightbours(p), [p]):
+            if n in seen:
+                continue
+            seen |= {n}
+            active = n in grid
+            num_neighbours = count_neighbours(n)
+
+            if active and num_neighbours in [2, 3]:
+                new_grid |= {n}
+            elif active:
+                continue
+            elif num_neighbours == 3:
+                new_grid |= {n}
+            else:
+                continue
+
+    return new_grid
+
+
+def solve(grid: Grid) -> int:
+
+    for __ in range(6):
+        grid = update(grid)
+
+    return len(grid)
+
+
+def main() -> None:
+    input = [line.strip() for line in sys.stdin.readlines()]
+    print(
+        solve(
+            {
+                (i, j, 0)
+                for i, line in enumerate(input)
+                for j, x in enumerate(line)
+                if x == "#"
+            }
+        )
+    )
+
+
+if __name__ == "__main__":
+    main()