85 lines
3.3 KiB
Plaintext
85 lines
3.3 KiB
Plaintext
Advent of Code
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--- Day 25: Clock Signal ---
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You open the door and find yourself on the roof. The city sprawls away from
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you for miles and miles.
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There's not much time now - it's already Christmas, but you're nowhere near
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the North Pole, much too far to deliver these stars to the sleigh in time.
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However, maybe the huge antenna up here can offer a solution. After all, the
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sleigh doesn't need the stars, exactly; it needs the timing data they
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provide, and you happen to have a massive signal generator right here.
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You connect the stars you have to your prototype computer, connect that to
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the antenna, and begin the transmission.
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Nothing happens.
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You call the service number printed on the side of the antenna and quickly
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explain the situation. "I'm not sure what kind of equipment you have
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connected over there," he says, "but you need a clock signal." You try to
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explain that this is a signal for a clock.
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"No, no, a clock signal - timing information so the antenna computer knows
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how to read the data you're sending it. An endless, alternating pattern of
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0, 1, 0, 1, 0, 1, 0, 1, 0, 1...." He trails off.
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You ask if the antenna can handle a clock signal at the frequency you would
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need to use for the data from the stars. "There's no way it can! The only
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antenna we've installed capable of that is on top of a top-secret Easter
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Bunny installation, and you're definitely not-" You hang up the phone.
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You've extracted the antenna's clock signal generation assembunny code (your
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puzzle input); it looks mostly compatible with code you worked on just
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recently.
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This antenna code, being a signal generator, uses one extra instruction:
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• out x transmits x (either an integer or the value of a register) as the
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next value for the clock signal.
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The code takes a value (via register a) that describes the signal to
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generate, but you're not sure how it's used. You'll have to find the input
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to produce the right signal through experimentation.
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What is the lowest positive integer that can be used to initialize register
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a and cause the code to output a clock signal of 0, 1, 0, 1... repeating
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forever?
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Your puzzle answer was 175.
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--- Part Two ---
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The antenna is ready. Now, all you need is the fifty stars required to
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generate the signal for the sleigh, but you don't have enough.
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You look toward the sky in desperation... suddenly noticing that a lone star
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has been installed at the top of the antenna! Only 49 more to go.
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If you like, you can [ [Retransmit the Signal] ] .
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Both parts of this puzzle are complete! They provide two gold stars: **
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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/2016/sponsors
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. http://adventofcode.com/2016/sponsors
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. https://en.wikipedia.org/wiki/Clock_signal
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. http://adventofcode.com/2016/day/12
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. http://adventofcode.com/2016/day/23
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. http://adventofcode.com/2016
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. http://adventofcode.com/2016/day/25/input
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