105 lines
3.4 KiB
Plaintext
105 lines
3.4 KiB
Plaintext
Advent of Code
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--- Day 24: Electromagnetic Moat ---
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The CPU itself is a large, black building surrounded by a bottomless pit.
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Enormous metal tubes extend outward from the side of the building at regular
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intervals and descend down into the void. There's no way to cross, but you
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need to get inside.
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No way, of course, other than building a bridge out of the magnetic
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components strewn about nearby.
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Each component has two ports, one on each end. The ports come in all
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different types, and only matching types can be connected. You take an
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inventory of the components by their port types (your puzzle input). Each
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port is identified by the number of pins it uses; more pins mean a stronger
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connection for your bridge. A 3/7 component, for example, has a type-3 port
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on one side, and a type-7 port on the other.
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Your side of the pit is metallic; a perfect surface to connect a magnetic,
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zero-pin port. Because of this, the first port you use must be of type 0. It
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doesn't matter what type of port you end with; your goal is just to make the
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bridge as strong as possible.
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The strength of a bridge is the sum of the port types in each component. For
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example, if your bridge is made of components 0/3, 3/7, and 7/4, your bridge
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has a strength of 0+3 + 3+7 + 7+4 = 24.
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For example, suppose you had the following components:
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0/2
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2/2
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2/3
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3/4
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3/5
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0/1
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10/1
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9/10
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With them, you could make the following valid bridges:
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• 0/1
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• 0/1--10/1
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• 0/1--10/1--9/10
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• 0/2
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• 0/2--2/3
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• 0/2--2/3--3/4
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• 0/2--2/3--3/5
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• 0/2--2/2
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• 0/2--2/2--2/3
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• 0/2--2/2--2/3--3/4
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• 0/2--2/2--2/3--3/5
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(Note how, as shown by 10/1, order of ports within a component doesn't
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matter. However, you may only use each port on a component once.)
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Of these bridges, the strongest one is 0/1--10/1--9/10; it has a strength of
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0+1 + 1+10 + 10+9 = 31.
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What is the strength of the strongest bridge you can make with the
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components you have available?
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Your puzzle answer was 1868.
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--- Part Two ---
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The bridge you've built isn't long enough; you can't jump the rest of the way.
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In the example above, there are two longest bridges:
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• 0/2--2/2--2/3--3/4
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• 0/2--2/2--2/3--3/5
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Of them, the one which uses the 3/5 component is stronger; its strength is
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0+2 + 2+2 + 2+3 + 3+5 = 19.
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What is the strength of the longest bridge you can make? If you can make
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multiple bridges of the longest length, pick the strongest one.
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Your puzzle answer was 1841.
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Both parts of this puzzle are complete! They provide two gold stars: **
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At this point, all that is left is for you to admire your advent calendar.
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If you still want to see it, you can get your puzzle input.
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References
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Visible links
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. http://adventofcode.com/
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. http://adventofcode.com/2017
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. http://adventofcode.com/2017/day/24/input
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