From 5b4e79cc749bd2d6451dc0b1fb03f5b500eb8873 Mon Sep 17 00:00:00 2001
From: Tom van der Lee <tom@vanderlee.io>
Date: Mon, 13 Dec 2021 19:18:02 +0100
Subject: Day 13

---
 day13/__init__.py | 109 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 109 insertions(+)
 create mode 100644 day13/__init__.py

(limited to 'day13/__init__.py')

diff --git a/day13/__init__.py b/day13/__init__.py
new file mode 100644
index 0000000..41b81dc
--- /dev/null
+++ b/day13/__init__.py
@@ -0,0 +1,109 @@
+import re
+from abc import ABC
+from copy import copy
+from dataclasses import dataclass
+from typing import List, Tuple, Union, TypedDict
+
+from aoc import BaseAssignment
+
+Coordinate = Tuple[int, int]
+
+def mirrored_index(index: int, fold: int) -> int:
+    return fold + (fold - index)
+
+@dataclass
+class Sheet:
+    dots: List[Coordinate]
+    width: int = 0
+    height: int = 0
+
+    def __post_init__(self):
+        x_coordinates, y_coordinates = zip(*self.dots)
+
+        self.width = max(x_coordinates) + 1
+        self.height = max(y_coordinates) + 1
+
+
+    def fold_x(self, position: int):
+        for x, y in copy(self.dots):
+            mirrored_x = mirrored_index(x, position)
+            if mirrored_x < position:
+                self.dots.append((mirrored_x, y))
+                self.dots.remove((x, y))
+
+        self.width = self.width // 2
+        self.dots = list(set(self.dots))
+
+    def fold_y(self, position: int):
+        for x, y in copy(self.dots):
+            mirrored_y = mirrored_index(y, position)
+            if mirrored_y < position:
+                self.dots.append((x, mirrored_y))
+                self.dots.remove((x, y))
+
+        self.height = self.height // 2
+        self.dots = list(set(self.dots))
+
+    def __repr__(self):
+        dots = set(self.dots)
+        return '\n'.join([
+            '',
+            *[
+                ''.join([
+                    '█' if (x, y) in dots else ' '
+                    for x in range(self.width)
+                ])
+                for y in range(self.height)
+            ],
+            '',
+        ])
+
+class Instruction(TypedDict):
+    direction: str
+    position: int
+
+coordinate_regex = re.compile('(\d+),(\d+)')
+instruction_regex = re.compile('fold along (?P<direction>[xy])=(?P<position>\d+)')
+
+class Assignment(BaseAssignment, ABC):
+    def parse_item(self, item: str) -> Union[Coordinate,Instruction]:
+        if coordinate := coordinate_regex.match(item):
+            return tuple(int(i) for i in coordinate.groups())
+
+        if instruction := instruction_regex.match(item):
+            return {
+                **instruction.groupdict(),
+                'position': int(instruction.groupdict()['position'])
+            }
+
+    def read_input(self, example = False) -> Tuple[Sheet, List[Instruction]]:
+        input = super().read_input(example)
+
+        coordinates: List[Coordinate] = []
+
+        while True:
+            coordinate = next(input)
+            if coordinate is None:
+                break
+
+            coordinates.append(coordinate)
+
+        sheet = Sheet(dots=coordinates)
+
+        return sheet, list(input)
+
+
+class AssignmentOne(Assignment):
+    example_result = 17
+
+    def run(self, input: Tuple[Sheet, List[Instruction]]) -> int:
+        sheet, instructions = input
+        getattr(sheet, f'fold_{instructions[0]["direction"]}')(instructions[0]["position"])
+        return len(sheet.dots)
+
+class AssignmentTwo(Assignment):
+    def run(self, input: Tuple[Sheet, List[Instruction]]) -> Sheet:
+        sheet, instructions = input
+        for instruction in instructions:
+            getattr(sheet, f'fold_{instruction["direction"]}')(instruction["position"])
+        return sheet
-- 
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