96 lines
2.8 KiB
Python
96 lines
2.8 KiB
Python
from __future__ import annotations
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from dataclasses import dataclass
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from typing import Iterator, Self
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day_num = 5
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def part1(lines: Iterator[str]) -> str:
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crane = Crane.parse(lines, False)
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crates = crane.perform_all_moves()
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return Crane.top(crates)
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def part2(lines: Iterator[str]) -> str:
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crane = Crane.parse(lines, True)
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crates = crane.perform_all_moves()
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return Crane.top(crates)
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@dataclass(slots=True, frozen=True)
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class Move:
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amount: int
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frm: int
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to: int
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@classmethod
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def parse(cls, line: str) -> Self:
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match line.split():
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case ['move', amount, 'from', frm, 'to', to]:
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return cls(int(amount), int(frm) - 1, int(to) - 1)
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case _:
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raise Exception("Not a valid move")
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def do_move(self, crates: list[str], as_9001: bool) -> list[str]:
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"""
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Moves the given crates by the provided move. Will fail if there are not enough crates
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in the stack to take crates off
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"""
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if as_9001:
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crates[self.to] += crates[self.frm][-self.amount:]
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else:
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crates[self.to] += crates[self.frm][-self.amount:][::-1]
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crates[self.frm] = crates[self.frm][:-self.amount]
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return crates
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@dataclass(slots=True, frozen=True)
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class Crane:
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stacks: list[str]
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moves: list[Move]
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is_9001: bool
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@classmethod
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def parse_crate_row(cls, line: str) -> list[None | str]:
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result: list[str | None] = []
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for c in line[1::4]:
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if c.isalnum():
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result.append(c)
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else:
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result.append(None)
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return result
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@classmethod
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def parse_stacks(cls, lines: Iterator[str]) -> list[str]:
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stacks: list[str] = []
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for line in lines:
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if not line:
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return stacks
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crate_row = Crane.parse_crate_row(line)
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if len(stacks) < len(crate_row):
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stacks += [""] * (len(crate_row) - len(stacks))
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for stack_num, crate in enumerate(crate_row):
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if crate is not None:
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stacks[stack_num] = crate + stacks[stack_num]
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raise Exception("Can never happen")
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@classmethod
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def parse(cls, lines: Iterator[str], is_9001: bool) -> Self:
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drawing = cls.parse_stacks(lines)
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moves = [Move.parse(line) for line in lines]
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return cls(drawing, moves, is_9001)
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@classmethod
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def top(cls, crates: list[str]) -> str:
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""" Lists the last item in the given stacks. Fails if any stack is empty """
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return ''.join(stack[-1] for stack in crates)
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def perform_all_moves(self) -> list[str]:
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stacks = self.stacks
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for move in self.moves:
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stacks = move.do_move(stacks, self.is_9001)
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return stacks
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