From b3f39262feb51295e8e6a8db938b5e327d9955ec Mon Sep 17 00:00:00 2001
From: Bruno BELANYI <bruno@belanyi.fr>
Date: Sun, 11 May 2025 22:33:11 +0100
Subject: [PATCH] 2017: d22: ex2: add solution

---
 2017/d22/ex2/ex2.py | 96 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 96 insertions(+)
 create mode 100755 2017/d22/ex2/ex2.py

diff --git a/2017/d22/ex2/ex2.py b/2017/d22/ex2/ex2.py
new file mode 100755
index 0000000..b4e6a62
--- /dev/null
+++ b/2017/d22/ex2/ex2.py
@@ -0,0 +1,96 @@
+#!/usr/bin/env python
+
+import collections
+import dataclasses
+import enum
+import sys
+from typing import NamedTuple
+
+
+class Point(NamedTuple):
+    x: int
+    y: int
+
+
+class Direction(enum.Enum):
+    UP = Point(-1, 0)
+    DOWN = Point(1, 0)
+    LEFT = Point(0, -1)
+    RIGHT = Point(0, 1)
+
+    def left(self) -> "Direction":
+        x, y = self.value
+        return Direction(Point(-y, x))
+
+    def right(self) -> "Direction":
+        x, y = self.value
+        return Direction(Point(y, -x))
+
+    def flip(self) -> "Direction":
+        x, y = self.value
+        return Direction(Point(-x, -y))
+
+    def apply(self, p: Point) -> Point:
+        dx, dy = self.value
+        return Point(p.x + dx, p.y + dy)
+
+
+class State(enum.StrEnum):
+    CLEAN = "."
+    WEAKENED = "W"
+    FLAGGED = "F"
+    INFECTED = "#"
+
+
+@dataclasses.dataclass
+class Carrier:
+    pos: Point
+    dir: Direction
+
+    def burst(self, infected: dict[Point, State]) -> bool:
+        infect = False
+        match infected[self.pos]:
+            case State.CLEAN:
+                self.dir = self.dir.left()
+                infected[self.pos] = State.WEAKENED
+            case State.WEAKENED:
+                infected[self.pos] = State.INFECTED
+                infect = True
+            case State.FLAGGED:
+                self.dir = self.dir.flip()
+                infected[self.pos] = State.CLEAN
+            case State.INFECTED:
+                self.dir = self.dir.right()
+                infected[self.pos] = State.FLAGGED
+        self.pos = self.dir.apply(self.pos)
+        return infect
+
+
+def solve(input: str) -> int:
+    def parse(input: str) -> set[Point]:
+        return {
+            Point(x, y)
+            for x, line in enumerate(input.splitlines())
+            for y, c in enumerate(line)
+            if c == "#"
+        }
+
+    infected: dict[Point, State] = collections.defaultdict(lambda: State.CLEAN)
+    for p in parse(input):
+        infected[p] = State.INFECTED
+    middle = len(input.splitlines()) // 2
+    carrier = Carrier(Point(middle, middle), Direction.UP)
+    total = 0
+
+    for _ in range(10000000):
+        total += carrier.burst(infected)
+    return total
+
+
+def main() -> None:
+    input = sys.stdin.read()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()