55 lines
1.6 KiB
Python
55 lines
1.6 KiB
Python
from __future__ import annotations
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from typing import Iterator
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day_num = 3
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def part1(lines: Iterator[str]) -> int:
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return sum(Rucksack.find_double(line) for line in lines)
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def part2(lines: Iterator[str]) -> int:
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groups = [lines] * 3
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zipped = zip(*groups, strict=True)
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return sum(Rucksack.find_common(group) for group in zipped)
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class Rucksack:
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@staticmethod
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def priority(char: str) -> int:
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"""
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Returns the priority given to each item.
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It is assumed, that we are given a valid item
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"""
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num = ord(char)
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if ord('a') <= num and num <= ord('z'):
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return num - ord('a') + 1
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if ord('A') <= num and num <= ord('Z'):
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return num - ord('A') + 27
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raise Exception(f"Unknown char: {char}")
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@staticmethod
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def find_double(rucksack: str) -> int:
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"""
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Finds the priority of the one item in both compartments.
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It is assumed that there is only one such item
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"""
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half = len(rucksack) // 2
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first = rucksack[:half]
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second = rucksack[half:]
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for item in first:
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if item in second:
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return Rucksack.priority(item)
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raise Exception("No double item")
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@staticmethod
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def find_common(group: tuple[str, ...]) -> int:
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"""
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Finds the one item in all three rucksacks given.
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It is assumed that there is only one such item and group has exactly three rucksacks
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"""
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for item in group[0]:
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if item in group[1] and item in group[2]:
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return Rucksack.priority(item)
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raise Exception("No common item found")
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