88 lines
3.4 KiB
Python
88 lines
3.4 KiB
Python
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"""
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--- Day 3: Rucksack Reorganization ---
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One Elf has the important job of loading all of the rucksacks with
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supplies for the jungle journey. Unfortunately, that Elf didn't quite
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follow the packing instructions, and so a few items now need to be
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rearranged.
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Each rucksack has two large compartments. All items of a given type are
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meant to go into exactly one of the two compartments. The Elf that did
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the packing failed to follow this rule for exactly one item type per
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rucksack.
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The Elves have made a list of all of the items currently in each
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rucksack (your puzzle input), but they need your help finding the
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errors. Every item type is identified by a single lowercase or
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uppercase letter (that is, a and A refer to different types of items).
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The list of items for each rucksack is given as characters all on a
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single line. A given rucksack always has the same number of items in
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each of its two compartments, so the first half of the characters
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represent items in the first compartment, while the second half of the
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characters represent items in the second compartment.
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For example, suppose you have the following list of contents from six
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rucksacks:
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vJrwpWtwJgWrhcsFMMfFFhFp
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jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL
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PmmdzqPrVvPwwTWBwg
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wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
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ttgJtRGJQctTZtZT
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CrZsJsPPZsGzwwsLwLmpwMDw
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- The first rucksack contains the items vJrwpWtwJgWrhcsFMMfFFhFp, which
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means its first compartment contains the items vJrwpWtwJgWr, while
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the second compartment contains the items hcsFMMfFFhFp. The only item
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type that appears in both compartments is lowercase p.
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- The second rucksack's compartments contain jqHRNqRjqzjGDLGL and
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rsFMfFZSrLrFZsSL. The only item type that appears in both compartments
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is uppercase L.
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- The third rucksack's compartments contain PmmdzqPrV and vPwwTWBwg;
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the only common item type is uppercase P.
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- The fourth rucksack's compartments only share item type v.
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- The fifth rucksack's compartments only share item type t.
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- The sixth rucksack's compartments only share item type s.
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To help prioritize item rearrangement, every item type can be converted
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to a priority:
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- Lowercase item types a through z have priorities 1 through 26.
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- Uppercase item types A through Z have priorities 27 through 52.
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In the above example, the priority of the item type that appears in
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both compartments of each rucksack is 16 (p), 38 (L), 42 (P), 22 (v),
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20 (t), and 19 (s); the sum of these is 157.
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Find the item type that appears in both compartments of each rucksack.
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What is the sum of the priorities of those item types?
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"""
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import string
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def main():
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total_priority = 0
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priority_index = f"{string.ascii_lowercase}{string.ascii_uppercase}"
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with open("input.txt", "r", encoding="utf-8") as f:
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for line in f:
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line_contents = line.strip()
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if not line_contents:
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continue
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total_item_count = len(line_contents)
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half_item_count = int(total_item_count/2)
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small_compartment_contents = list(line_contents[:half_item_count])
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large_compartment_contents = list(line_contents[half_item_count:])
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common_item = set(small_compartment_contents).intersection(set(large_compartment_contents)).pop()
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common_item_priority = priority_index.index(common_item) + 1
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total_priority += common_item_priority
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print(f"Total priority is {total_priority}")
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if __name__ == "__main__":
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main()
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