52 lines
1.4 KiB
Python
52 lines
1.4 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(priority(find_double(line)) for line in lines)
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def part2(lines: Iterator[str]) -> int:
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groups = zip(lines, lines, lines, strict=True)
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return sum(priority(find_common_item(group)) for group in groups)
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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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if 'a' <= char and char <= 'z':
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return ord(char) - ord('a') + 1
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if 'A' <= char and char <= 'Z':
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return ord(char) - ord('A') + 27
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raise Exception(f"Unknown char: {char}")
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def find_double(rucksack: str) -> str:
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"""
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Finds 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 item
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raise Exception("No double item")
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def find_common_item(group: tuple[str, str, str]) -> str:
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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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first, second, third = group
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for item in first:
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if item in second and item in third:
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return item
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raise Exception("No common item found")
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