From 050cd4e1bea0bf6a0dd2d186ab428bc88ab0959b Mon Sep 17 00:00:00 2001
From: Sijmen Schoon <me@sijmenschoon.nl>
Date: Fri, 25 Dec 2020 02:14:18 +0100
Subject: [PATCH] python(day24): Day24 hype, all caught up

---
 python/day24.py | 81 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100644 python/day24.py

diff --git a/python/day24.py b/python/day24.py
new file mode 100644
index 0000000..27b5373
--- /dev/null
+++ b/python/day24.py
@@ -0,0 +1,81 @@
+import fileinput
+import itertools
+from pprint import pprint
+from typing import Any, Dict, List, Optional, Tuple, Generator
+
+
+def parse() -> Generator[List[str], None, None]:
+    for line in fileinput.input():
+        line = line.strip()
+        directions = []
+        while line:
+            for direction in ("e", "se", "sw", "w", "nw", "ne"):
+                if line.startswith(direction):
+                    line = line[len(direction) :]
+                    directions.append(direction)
+                    break
+        yield directions
+
+
+def main() -> None:
+    directions = list(parse())
+
+    N = 1000
+    OFFSET = N // 2
+    grid = [[False] * N for _ in range(N)]
+
+    for tile in directions:
+        column, row = 0, 0
+        for direction in tile:
+            if direction == "e":
+                column += 1
+            elif direction == "se":
+                column += row % 2
+                row += 1
+            elif direction == "sw":
+                column -= (row + 1) % 2
+                row += 1
+            elif direction == "w":
+                column -= 1
+            elif direction == "nw":
+                column -= (row + 1) % 2
+                row -= 1
+            elif direction == "ne":
+                column += row % 2
+                row -= 1
+        grid[row + OFFSET][column + OFFSET] = not grid[row + OFFSET][column + OFFSET]
+    print("Part 1:", sum(sum(row) for row in grid))
+
+    changes = []
+    for _ in range(100):
+        for row in range(N):
+            for column in range(N):
+                neighbors = 0
+                for dc, dr in (
+                    (1, 0),
+                    (row % 2, 1),
+                    (-((row + 1) % 2), 1),
+                    (-1, 0),
+                    (-((row + 1) % 2), -1),
+                    (row % 2, -1),
+                ):
+                    c, r = column + dc, row + dr
+                    if 0 <= c < N and 0 <= r < N:
+                        neighbors += grid[r][c]
+
+                # print(neighbors)
+                if grid[row][column]:
+                    if neighbors != 1 and neighbors != 2:
+                        changes.append((row, column, False))
+                else:
+                    if neighbors == 2:
+                        changes.append((row, column, True))
+
+        for (row, column, value) in changes:
+            grid[row][column] = value
+        changes.clear()
+
+    print("Part 2:", sum(sum(row) for row in grid))
+
+if __name__ == "__main__":
+    main()