2017: d24: ex1: add solution

2017/d24/ex1/ex1.py

@@ -0,0 +1,49 @@
+#!/usr/bin/env python
+
+import functools
+import sys
+from typing import NamedTuple
+
+
+class Component(NamedTuple):
+    left: int
+    right: int
+
+    @classmethod
+    def from_str(cls, input: str) -> "Component":
+        return cls(*map(int, input.split("/")))
+
+    def remaining_port(self, connection: int) -> int:
+        if connection == self.left:
+            return self.right
+        elif connection == self.right:
+            return self.left
+        assert False  # Sanity check
+
+
+def solve(input: str) -> int:
+    def parse(input: str) -> list[Component]:
+        return [Component.from_str(line) for line in input.splitlines()]
+
+    @functools.cache
+    def strongest_bridge(start: int, components: frozenset[Component]) -> int:
+        candidates = {c for c in components if start in c}
+        if not candidates:
+            return 0
+        return max(
+            sum(c) + strongest_bridge(c.remaining_port(start), components - {c})
+            for c in candidates
+        )
+
+    components = parse(input)
+    assert len(set(components)) == len(components)  # Sanity check
+    return strongest_bridge(0, frozenset(components))
+
+
+def main() -> None:
+    input = sys.stdin.read()
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()