62 lines
3.5 KiB
Plaintext
62 lines
3.5 KiB
Plaintext
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--- Day 7: Handy Haversacks ---
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You land at the regional airport in time for your next flight. In fact, it looks like you'll even have time to grab some food: all flights are currently delayed due to issues in luggage processing.
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Due to recent aviation regulations, many rules (your puzzle input) are being enforced about bags and their contents; bags must be color-coded and must contain specific quantities of other color-coded bags. Apparently, nobody responsible for these regulations considered how long they would take to enforce!
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For example, consider the following rules:
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light red bags contain 1 bright white bag, 2 muted yellow bags.
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dark orange bags contain 3 bright white bags, 4 muted yellow bags.
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bright white bags contain 1 shiny gold bag.
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muted yellow bags contain 2 shiny gold bags, 9 faded blue bags.
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shiny gold bags contain 1 dark olive bag, 2 vibrant plum bags.
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dark olive bags contain 3 faded blue bags, 4 dotted black bags.
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vibrant plum bags contain 5 faded blue bags, 6 dotted black bags.
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faded blue bags contain no other bags.
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dotted black bags contain no other bags.
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These rules specify the required contents for 9 bag types. In this example, every faded blue bag is empty, every vibrant plum bag contains 11 bags (5 faded blue and 6 dotted black), and so on.
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You have a shiny gold bag. If you wanted to carry it in at least one other bag, how many different bag colors would be valid for the outermost bag? (In other words: how many colors can, eventually, contain at least one shiny gold bag?)
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In the above rules, the following options would be available to you:
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A bright white bag, which can hold your shiny gold bag directly.
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A muted yellow bag, which can hold your shiny gold bag directly, plus some other bags.
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A dark orange bag, which can hold bright white and muted yellow bags, either of which could then hold your shiny gold bag.
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A light red bag, which can hold bright white and muted yellow bags, either of which could then hold your shiny gold bag.
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So, in this example, the number of bag colors that can eventually contain at least one shiny gold bag is 4.
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How many bag colors can eventually contain at least one shiny gold bag? (The list of rules is quite long; make sure you get all of it.)
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--- Part Two ---
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It's getting pretty expensive to fly these days - not because of ticket prices, but because of the ridiculous number of bags you need to buy!
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Consider again your shiny gold bag and the rules from the above example:
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faded blue bags contain 0 other bags.
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dotted black bags contain 0 other bags.
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vibrant plum bags contain 11 other bags: 5 faded blue bags and 6 dotted black bags.
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dark olive bags contain 7 other bags: 3 faded blue bags and 4 dotted black bags.
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So, a single shiny gold bag must contain 1 dark olive bag (and the 7 bags within it) plus 2 vibrant plum bags (and the 11 bags within each of those): 1 + 1*7 + 2 + 2*11 = 32 bags!
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Of course, the actual rules have a small chance of going several levels deeper than this example; be sure to count all of the bags, even if the nesting becomes topologically impractical!
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Here's another example:
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shiny gold bags contain 2 dark red bags.
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dark red bags contain 2 dark orange bags.
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dark orange bags contain 2 dark yellow bags.
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dark yellow bags contain 2 dark green bags.
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dark green bags contain 2 dark blue bags.
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dark blue bags contain 2 dark violet bags.
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dark violet bags contain no other bags.
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In this example, a single shiny gold bag must contain 126 other bags.
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How many individual bags are required inside your single shiny gold bag?
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