85 lines
4.5 KiB
Plaintext
85 lines
4.5 KiB
Plaintext
Advent of Code
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--- Day 23: Category Six ---
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The droids have finished repairing as much of the ship as they can. Their report indicates that this was a Category 6
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disaster - not because it was that bad, but because it destroyed the stockpile of Category 6 network cables as well as most
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of the ship's network infrastructure.
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You'll need to rebuild the network from scratch.
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The computers on the network are standard Intcode computers that communicate by sending packets to each other. There are 50
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of them in total, each running a copy of the same Network Interface Controller (NIC) software (your puzzle input). The
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computers have network addresses 0 through 49; when each computer boots up, it will request its network address via a single
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input instruction. Be sure to give each computer a unique network address.
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Once a computer has received its network address, it will begin doing work and communicating over the network by sending and
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receiving packets. All packets contain two values named X and Y. Packets sent to a computer are queued by the recipient and
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read in the order they are received.
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To send a packet to another computer, the NIC will use three output instructions that provide the destination address of the
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packet followed by its X and Y values. For example, three output instructions that provide the values 10, 20, 30 would send a
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packet with X=20 and Y=30 to the computer with address 10.
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To receive a packet from another computer, the NIC will use an input instruction. If the incoming packet queue is empty,
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provide -1. Otherwise, provide the X value of the next packet; the computer will then use a second input instruction to
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receive the Y value for the same packet. Once both values of the packet are read in this way, the packet is removed from the
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queue.
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Note that these input and output instructions never block. Specifically, output instructions do not wait for the sent packet
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to be received - the computer might send multiple packets before receiving any. Similarly, input instructions do not wait for
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a packet to arrive - if no packet is waiting, input instructions should receive -1.
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Boot up all 50 computers and attach them to your network. What is the Y value of the first packet sent to address 255?
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Your puzzle answer was 19530.
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--- Part Two ---
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Packets sent to address 255 are handled by a device called a NAT (Not Always Transmitting). The NAT is responsible for
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managing power consumption of the network by blocking certain packets and watching for idle periods in the computers.
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If a packet would be sent to address 255, the NAT receives it instead. The NAT remembers only the last packet it receives;
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that is, the data in each packet it receives overwrites the NAT's packet memory with the new packet's X and Y values.
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The NAT also monitors all computers on the network. If all computers have empty incoming packet queues and are continuously
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trying to receive packets without sending packets, the network is considered idle.
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Once the network is idle, the NAT sends only the last packet it received to address 0; this will cause the computers on the
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network to resume activity. In this way, the NAT can throttle power consumption of the network when the ship needs power in
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other areas.
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Monitor packets released to the computer at address 0 by the NAT. What is the first Y value delivered by the NAT to the
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computer at address 0 twice in a row?
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Your puzzle answer was 12725.
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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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. https://adventofcode.com/
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. https://adventofcode.com/2019/about
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. https://adventofcode.com/2019/events
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. https://adventofcode.com/2019/settings
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. https://adventofcode.com/2019/auth/logout
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. Advent of Code Supporter
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https://adventofcode.com/2019/support
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. https://adventofcode.com/2019
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. https://adventofcode.com/2019
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. https://adventofcode.com/2019/support
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. https://adventofcode.com/2019/sponsors
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. https://adventofcode.com/2019/leaderboard
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. https://adventofcode.com/2019/stats
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. https://adventofcode.com/2019/sponsors
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. https://en.wikipedia.org/wiki/Category_6_cable
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. https://adventofcode.com/2019/day/9
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. https://en.wikipedia.org/wiki/Blocking_(computing)
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. https://adventofcode.com/2019
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. https://adventofcode.com/2019/day/23/input
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