2021: d19: ex2: add solution

2021/d19/ex2/ex2.py

@@ -0,0 +1,179 @@
+#!/usr/bin/env python
+
+import functools
+import itertools
+import sys
+from dataclasses import dataclass
+from typing import List, Optional, Set, Tuple
+
+
+@dataclass(eq=True, frozen=True)  # Hash-able
+class Vector:
+    x: int
+    y: int
+    z: int
+
+    def __add__(self, other: "Vector") -> "Vector":
+        return Vector(self.x + other.x, self.y + other.y, self.z + other.z)
+
+    def __sub__(self, other: "Vector") -> "Vector":
+        return Vector(self.x - other.x, self.y - other.y, self.z - other.z)
+
+
+@dataclass(eq=True, frozen=True)  # Hash-able
+class Matrix:
+    v1: Vector
+    v2: Vector
+    v3: Vector
+
+    def __matmul__(self, other: Vector) -> Vector:
+        return Vector(
+            self.v1.x * other.x + self.v1.y * other.y + self.v1.z * other.z,
+            self.v2.x * other.x + self.v2.y * other.y + self.v2.z * other.z,
+            self.v3.x * other.x + self.v3.y * other.y + self.v3.z * other.z,
+        )
+
+
+def rotations() -> List[Matrix]:
+    def cos(angle: int) -> int:
+        if angle == 0:
+            return 1
+        if angle == 180:
+            return -1
+        assert angle in (90, 270)  # Sanity check
+        return 0
+
+    def sin(angle: int) -> int:
+        if angle == 90:
+            return 1
+        if angle == 270:
+            return -1
+        assert angle in (0, 180)  # Sanity check
+        return 0
+
+    def rotate(x: int, y: int, z: int) -> Matrix:
+        v1 = Vector(
+            cos(z) * cos(y),
+            cos(z) * sin(y) * sin(x) - sin(z) * cos(x),
+            cos(z) * sin(y) * cos(x) + sin(z) * sin(x),
+        )
+        v2 = Vector(
+            sin(z) * cos(y),
+            sin(z) * sin(y) * sin(x) + cos(z) * cos(x),
+            sin(z) * sin(y) * cos(x) - cos(z) * sin(x),
+        )
+        v3 = Vector(-sin(y), cos(y) * sin(x), cos(y) * cos(x))
+        return Matrix(v1, v2, v3)
+
+    return [
+        rotate(0, 0, 0),
+        rotate(90, 0, 0),
+        rotate(180, 0, 0),
+        rotate(270, 0, 0),
+        rotate(0, 90, 0),
+        rotate(90, 90, 0),
+        rotate(180, 90, 0),
+        rotate(270, 90, 0),
+        rotate(0, 180, 0),
+        rotate(90, 180, 0),
+        rotate(180, 180, 0),
+        rotate(270, 180, 0),
+        rotate(0, 270, 0),
+        rotate(90, 270, 0),
+        rotate(180, 270, 0),
+        rotate(270, 270, 0),
+        rotate(0, 0, 90),
+        rotate(90, 0, 90),
+        rotate(180, 0, 90),
+        rotate(270, 0, 90),
+        rotate(0, 0, 270),
+        rotate(90, 0, 270),
+        rotate(180, 0, 270),
+        rotate(270, 0, 270),
+    ]
+
+
+ROTATIONS = rotations()
+
+BeaconList = Set[Vector]
+
+
+def solve(input: List[str]) -> int:
+    def parse() -> List[BeaconList]:
+        res: List[BeaconList] = []
+
+        for line in input:
+            if "scanner" in line:
+                res.append(set())
+                continue
+            if line == "":
+                continue
+            x, y, z = map(int, line.split(","))
+            res[-1].add(Vector(x, y, z))
+
+        return res
+
+    def find_overlap(
+        known: BeaconList, other: BeaconList
+    ) -> Optional[Tuple[Matrix, Vector]]:
+        def find_delta(known: BeaconList, other: BeaconList) -> Optional[Vector]:
+            for dest, source in itertools.product(known, rotated):
+                delta = dest - source
+                if sum((v + delta) in known for v in rotated) >= 12:
+                    return delta
+            return None
+
+        for r in ROTATIONS:
+            rotated = set(r @ v for v in other)
+            if (delta := find_delta(known, rotated)) is not None:
+                return r, delta
+
+        return None
+
+    def apply(known: BeaconList, other: BeaconList) -> Tuple[bool, Vector, BeaconList]:
+        res = find_overlap(known, other)
+        if res is None:
+            return False, Vector(0, 0, 0), known
+
+        rot, delta = res
+
+        new = {(rot @ v) + delta for v in other}
+
+        # Return whether there are new points in the set
+        return (new <= known), delta, (known | new)
+
+    def match_all(scans: List[BeaconList]) -> Set[Vector]:
+        # First scan is our basis
+        known = scans[0]
+        # No need to inspect the first scan in the future
+        to_match = scans[1:]
+        # Position our first scanner at the origin
+        deltas = {Vector(0, 0, 0)}
+
+        while to_match:
+            s = to_match.pop(0)
+            applied, delta, known = apply(known, s)
+            if not applied:
+                to_match.append(s)
+            else:
+                deltas.add(delta)
+        return deltas
+
+    def manhattan_dist(v1: Vector, v2: Vector) -> int:
+        return abs(v1.x - v2.x) + abs(v1.y - v2.y) + abs(v1.z - v2.z)
+
+    beacons = parse()
+    scanner_positions = match_all(beacons)
+    return max(
+        manhattan_dist(v1, v2)
+        for v1, v2 in itertools.combinations(scanner_positions, 2)
+    )
+
+
+def main() -> None:
+    input = [line.strip() for line in sys.stdin.readlines()]
+    print(solve(input))
+
+
+if __name__ == "__main__":
+    main()