day 9

2022/09/python/main.py

@@ -0,0 +1,112 @@
+#!/usr/bin/env python
+
+from dataclasses import dataclass
+from os.path import dirname, join
+from typing import Literal
+
+# Day 09
+
+# Common
+
+
+def read_input(filename):
+    data = join(dirname(__file__), '..', filename)
+    with open(data) as f:
+        return f.read().strip()
+
+
+test = read_input('test.txt')
+data = read_input('input.txt')
+
+
+@dataclass(unsafe_hash=True)
+class Point:
+    x: int
+    y: int
+
+    def __add__(self, other: 'Point'):
+        return Point(self.x + other.x, self.y + other.y)
+
+    def __sub__(self, other: 'Point'):
+        return Point(self.x - other.x, self.y - other.y)
+
+    def distance(self, other: 'Point') -> int:
+        return max(abs(self.x - other.x), abs(self.y-other.y))
+
+    def normalise(self):
+        self.x = max(-1, min(1, self.x))
+        self.y = max(-1, min(1, self.y))
+        return self
+
+
+Directions = Literal['U', 'D', 'L', 'R']
+Instruction = tuple[Directions, int]
+
+MAPPING: dict[Directions, Point] = {'U': Point(0, 1), 'D': Point(0, -1), 'L': Point(-1, 0), 'R': Point(1, 0)}
+
+
+class Rope:
+    def __init__(self, instructions: list[Instruction], links: int) -> None:
+        self.instructions = instructions
+        start = Point(0, 0)
+        self.touched: set[Point] = set([start])
+        self.links = [start for _ in range(links)]
+
+    def move(self, instruction: Instruction):
+        direction, travel = instruction
+        last = len(self.links) - 1
+        for _ in range(travel):
+            moved: list[Point] = []
+            for i, link in enumerate(self.links):
+                if i == 0:
+                    link = link + MAPPING[direction]
+                else:
+                    head = moved[i-1]
+                    distance = head.distance(link)
+                    if distance > 1:
+                        link = link + (head - link).normalise()
+                moved.append(link)
+                if i == last:
+                    self.touched.add(link)
+            self.links = moved
+
+    def run(self):
+        for instruction in self.instructions:
+            self.move(instruction)
+        return len(self.touched)
+
+    @staticmethod
+    def visualise(points: list[Point], numbered=True) -> str:
+        """
+        Only used to visualise, not actual logic
+        """
+        max_x = max(p.x for p in points)
+        min_x = min(p.x for p in points)
+        max_y = max(p.y for p in points)
+        min_y = min(p.y for p in points)
+        range_x = max_x - min_x
+        range_y = max_y - min_y
+        grid = [
+            ['.' for _ in range(range_x+1)]
+            for _ in range(range_y+1)
+        ]
+        for i, link in enumerate(points):
+            row = grid[range_y-(link.y - min_y)]
+            if row[link.x-min_x] == '.':
+                row[link.x-min_x] = str(i) if numbered else "#"
+        return '\n'.join(map(lambda line: ''.join(line), grid))
+
+    @staticmethod
+    def parse(data: str, links: int):
+        instructions = [
+            (i[0], int(i[1]))
+            for i in map(lambda line: line.split(), data.splitlines())
+        ]
+        return Rope(instructions, links)
+
+
+# Running
+grid = Rope.parse(data, 2)
+print(grid.run())
+grid = Rope.parse(data, 10)
+print(grid.run())