day09 finished

README.md

@@ -8,6 +8,7 @@ I use python 3.11 without any libraries beyond the standard.
 
 | Day | Time      | Rank  | Score | Time     | Rank  | Score |
 | --- | --------- | ----- | ----- | -------- | ----- | ----- |
+|  9  | 00:54:18  |  7719 |     0 | 01:07:37 |  4901 |     0 |
 |  8  | 00:41:51  |  7831 |     0 | 00:59:27 |  6325 |     0 |
 |  7  | 00:34:59  |  2683 |     0 | 00:45:45 |  2943 |     0 |
 |  6  | 00:14:52  |  9153 |     0 | 00:17:06 |  8413 |     0 |

advent/days/day09/data/test01.txt

@@ -0,0 +1,8 @@
+R 4
+U 4
+L 3
+D 1
+R 4
+D 1
+L 5
+R 2

advent/days/day09/data/test02.txt

@@ -0,0 +1,8 @@
+R 5
+U 8
+L 8
+D 3
+R 17
+D 10
+L 25
+U 20

advent/days/day09/solution.py

@@ -0,0 +1,92 @@
+from __future__ import annotations
+from dataclasses import dataclass
+
+from typing import Iterator
+
+day_num = 9
+
+
+def part1(lines: Iterator[str]) -> int:
+    lst = [Command.parse(line) for line in lines]
+    return Command.walk(lst, 2)
+
+
+def part2(lines: Iterator[str]) -> int:
+    lst = [Command.parse(line) for line in lines]
+    return Command.walk(lst, 10)
+
+
+@dataclass(frozen=True, slots=True)
+class Point:
+    x: int
+    y: int
+
+    @staticmethod
+    def parse_direction(char: str) -> Point:
+        """ Parses the given direction to a Point. May raise if invalid """
+        match char:
+            case 'R':
+                return Point(1, 0)
+            case 'U':
+                return Point(0, 1)
+            case 'L':
+                return Point(-1, 0)
+            case 'D':
+                return Point(0, -1)
+            case _:
+                raise Exception(f"Unkown Direction: {char}")
+
+    def add(self, other: Point) -> Point:
+        return Point(self.x + other.x, self.y + other.y)
+
+    def sub(self, other: Point) -> Point:
+        return Point(self.x - other.x, self.y - other.y)
+
+    def is_unit(self) -> bool:
+        """ return true, if this discribes any point (diagonally) adjacent to the origin"""
+        return abs(self.x) <= 1 and abs(self.y) <= 1
+
+    def as_unit(self) -> Point:
+        """ Compresses this Point to a point with unit components """
+        def unit(num: int) -> int:
+            return 0 if num == 0 else num // abs(num)
+        return Point(unit(self.x), unit(self.y))
+
+    def step_to(self, other: Point) -> Point | None:
+        diff = other.sub(self)
+        if diff.is_unit():
+            return None
+        return self.add(diff.as_unit())
+
+
+@dataclass(frozen=True, slots=True)
+class Command:
+    dir: Point
+    steps: int
+
+    @staticmethod
+    def parse(line: str) -> Command:
+        """ Parse a command line. My raise exception if the was an illegal line"""
+        match line.split():
+            case [dir, steps]:
+                return Command(Point.parse_direction(dir), int(steps))
+            case _:
+                raise Exception(f"Illegal line: {line}")
+
+    @staticmethod
+    def walk(lst: list[Command], rope_length: int):
+        """ Walks the whole rope in Planck length steps """
+        rope = [Point(0, 0)] * rope_length
+        visited = {rope[-1]}
+        for command in lst:
+            for _ in range(command.steps):
+                rope[0] = rope[0].add(command.dir)
+                for n in range(1, rope_length):
+                    moved_piece = rope[n].step_to(rope[n - 1])
+                    if not moved_piece:
+                        break
+                    rope[n] = moved_piece
+                    if n == rope_length - 1:
+                        visited.add(rope[n])
+
+        return len(visited)

advent/days/day09/test_solution.py

@@ -0,0 +1,41 @@
+from advent.common import utils
+
+from .solution import Command, day_num, part1, part2
+
+
+def test_part1():
+    data = utils.read_data(day_num, 'test01.txt')
+    expected = 13
+    result = part1(data)
+    assert result == expected
+
+
+def test_part2():
+    data = utils.read_data(day_num, 'test02.txt')
+    expected = 36
+    result = part2(data)
+    assert result == expected
+
+
+def test_short():
+    data = utils.read_data(day_num, 'test01.txt')
+    expected = 13
+    lst = [Command.parse(line) for line in data]
+    result = Command.walk(lst, 2)
+    assert result == expected
+
+
+def test_long1():
+    data = utils.read_data(day_num, 'test01.txt')
+    expected = 1
+    lst = [Command.parse(line) for line in data]
+    result = Command.walk(lst, 10)
+    assert result == expected
+
+
+def test_long2():
+    data = utils.read_data(day_num, 'test02.txt')
+    expected = 36
+    lst = [Command.parse(line) for line in data]
+    result = Command.walk(lst, 10)
+    assert result == expected