123 lines
3.2 KiB
Python
123 lines
3.2 KiB
Python
"Day 3: Gear Ratios"
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from __future__ import annotations
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from collections import UserDict
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from dataclasses import dataclass
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from functools import reduce
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import math
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from typing import NamedTuple
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class Symbol(NamedTuple):
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value: str
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row: int
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col: int
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class Number(NamedTuple):
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value: str
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row: int
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col: int
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anchor: Symbol | None = None
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def extend_digit(self, digit: str) -> Number:
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return self._replace(value=self.value + digit)
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class Part(NamedTuple):
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number: Number
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symbol: Symbol
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@dataclass
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class Schematic:
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numbers: list[Number]
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symbols: list[Symbol]
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@classmethod
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def parse(cls, input: str) -> Schematic:
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row = 0
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col = 0
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current_number: Number | None = None
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numbers: list[Number] = []
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symbols: list[Symbol] = []
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for char in input:
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match char:
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# Digit
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case n if n in "0123456789":
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if not current_number:
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current_number = Number("", row, col)
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current_number = current_number.extend_digit(char)
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col += 1
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# Blank
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case ".":
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if current_number:
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numbers.append(current_number)
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current_number = None
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col += 1
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# Newline
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case "\n":
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if current_number:
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numbers.append(current_number)
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current_number = None
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row += 1
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col = 0
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# Schematic smybol
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case _:
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if current_number:
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numbers.append(current_number)
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current_number = None
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symbols.append(Symbol(char, row, col))
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col += 1
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# Finalize a number at the end of the schematic
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if current_number:
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numbers.append(current_number)
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return cls(numbers, symbols)
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def parts(self) -> set[Part]:
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return {
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Part(number, symbol)
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for number in self.numbers
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for symbol in self.symbols
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if (
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# Symbol within 1 row
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(number.row - 1 <= symbol.row <= number.row + 1)
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and
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# Symbol within 1 column
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(number.col - 1 <= symbol.col <= number.col + len(number.value))
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)
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}
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def part_groups(self) -> dict[Symbol, set[Part]]:
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groups: dict[Symbol, set[Part]] = {}
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for part in self.parts():
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if part.symbol not in groups:
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groups[part.symbol] = set()
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groups[part.symbol].add(part)
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return groups
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def solve_part_1(input: str) -> int:
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schematic = Schematic.parse(input)
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return sum(int(part.number.value) for part in schematic.parts())
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def solve_part_2(input: str) -> int:
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schematic = Schematic.parse(input)
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return sum(
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reduce(
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lambda x, y: x * y,
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(int(part.number.value) for part in parts),
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)
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for symbol, parts in schematic.part_groups().items()
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if symbol.value == "*"
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if len(parts) == 2
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)
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