112 lines
4.7 KiB
Plaintext
112 lines
4.7 KiB
Plaintext
# Advent of Code
|
||
|
||
--- Day 7: Handy Haversacks ---
|
||
|
||
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.
|
||
|
||
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!
|
||
|
||
For example, consider the following rules:
|
||
|
||
light red bags contain 1 bright white bag, 2 muted yellow bags.
|
||
dark orange bags contain 3 bright white bags, 4 muted yellow bags.
|
||
bright white bags contain 1 shiny gold bag.
|
||
muted yellow bags contain 2 shiny gold bags, 9 faded blue bags.
|
||
shiny gold bags contain 1 dark olive bag, 2 vibrant plum bags.
|
||
dark olive bags contain 3 faded blue bags, 4 dotted black bags.
|
||
vibrant plum bags contain 5 faded blue bags, 6 dotted black bags.
|
||
faded blue bags contain no other bags.
|
||
dotted black bags contain no other bags.
|
||
|
||
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.
|
||
|
||
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?)
|
||
|
||
In the above rules, the following options would be available to you:
|
||
|
||
• A bright white bag, which can hold your shiny gold bag directly.
|
||
• A muted yellow bag, which can hold your shiny gold bag directly, plus some other bags.
|
||
• A dark orange bag, which can hold bright white and muted yellow bags, either of which
|
||
could then hold your shiny gold bag.
|
||
• A light red bag, which can hold bright white and muted yellow bags, either of which
|
||
could then hold your shiny gold bag.
|
||
|
||
So, in this example, the number of bag colors that can eventually contain at least one
|
||
shiny gold bag is 4.
|
||
|
||
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.)
|
||
|
||
Your puzzle answer was 302.
|
||
|
||
The first half of this puzzle is complete! It provides one gold star: *
|
||
|
||
--- Part Two ---
|
||
|
||
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!
|
||
|
||
Consider again your shiny gold bag and the rules from the above example:
|
||
|
||
• faded blue bags contain 0 other bags.
|
||
• dotted black bags contain 0 other bags.
|
||
• vibrant plum bags contain 11 other bags: 5 faded blue bags and 6 dotted black bags.
|
||
• dark olive bags contain 7 other bags: 3 faded blue bags and 4 dotted black bags.
|
||
|
||
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!
|
||
|
||
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!
|
||
|
||
Here's another example:
|
||
|
||
shiny gold bags contain 2 dark red bags.
|
||
dark red bags contain 2 dark orange bags.
|
||
dark orange bags contain 2 dark yellow bags.
|
||
dark yellow bags contain 2 dark green bags.
|
||
dark green bags contain 2 dark blue bags.
|
||
dark blue bags contain 2 dark violet bags.
|
||
dark violet bags contain no other bags.
|
||
|
||
In this example, a single shiny gold bag must contain 126 other bags.
|
||
|
||
How many individual bags are required inside your single shiny gold bag?
|
||
|
||
Your puzzle answer was 4165.
|
||
|
||
Both parts of this puzzle are complete! They provide two gold stars: **
|
||
|
||
At this point, you should return to your Advent calendar and try another puzzle.
|
||
|
||
If you still want to see it, you can get your puzzle input.
|
||
|
||
References
|
||
|
||
Visible links
|
||
. https://adventofcode.com/
|
||
. https://adventofcode.com/2020/about
|
||
. https://adventofcode.com/2020/events
|
||
. https://adventofcode.com/2020/settings
|
||
. https://adventofcode.com/2020/auth/logout
|
||
. Advent of Code Supporter
|
||
https://adventofcode.com/2020/support
|
||
. https://adventofcode.com/2020
|
||
. https://adventofcode.com/2020
|
||
. https://adventofcode.com/2020/support
|
||
. https://adventofcode.com/2020/sponsors
|
||
. https://adventofcode.com/2020/leaderboard
|
||
. https://adventofcode.com/2020/stats
|
||
. https://adventofcode.com/2020/sponsors
|
||
. https://adventofcode.com/2020/day/7/input
|