2017-12-12 13:48:53 +00:00
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Advent of Code
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--- Day 12: Digital Plumber ---
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Walking along the memory banks of the stream, you find a small village that is experiencing a little confusion:
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some programs can't communicate with each other.
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Programs in this village communicate using a fixed system of pipes. Messages are passed between programs using
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these pipes, but most programs aren't connected to each other directly. Instead, programs pass messages between
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each other until the message reaches the intended recipient.
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For some reason, though, some of these messages aren't ever reaching their intended recipient, and the programs
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suspect that some pipes are missing. They would like you to investigate.
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You walk through the village and record the ID of each program and the IDs with which it can communicate directly
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(your puzzle input). Each program has one or more programs with which it can communicate, and these pipes are
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bidirectional; if 8 says it can communicate with 11, then 11 will say it can communicate with 8.
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You need to figure out how many programs are in the group that contains program ID 0.
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For example, suppose you go door-to-door like a travelling salesman and record the following list:
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0 <-> 2
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1 <-> 1
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2 <-> 0, 3, 4
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3 <-> 2, 4
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4 <-> 2, 3, 6
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5 <-> 6
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6 <-> 4, 5
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In this example, the following programs are in the group that contains program ID 0:
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• Program 0 by definition.
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• Program 2, directly connected to program 0.
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• Program 3 via program 2.
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• Program 4 via program 2.
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• Program 5 via programs 6, then 4, then 2.
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• Program 6 via programs 4, then 2.
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Therefore, a total of 6 programs are in this group; all but program 1, which has a pipe that connects it to
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itself.
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How many programs are in the group that contains program ID 0?
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2018-03-15 15:08:01 +00:00
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Your puzzle answer was 378.
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2017-12-12 13:48:53 +00:00
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The first half of this puzzle is complete! It provides one gold star: *
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--- Part Two ---
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There are more programs than just the ones in the group containing program ID 0. The rest of them have no way of
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reaching that group, and still might have no way of reaching each other.
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A group is a collection of programs that can all communicate via pipes either directly or indirectly. The
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programs you identified just a moment ago are all part of the same group. Now, they would like you to determine
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the total number of groups.
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In the example above, there were 2 groups: one consisting of programs 0,2,3,4,5,6, and the other consisting
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solely of program 1.
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How many groups are there in total?
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Although it hasn't changed, you can still get your puzzle input.
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2018-03-15 15:08:01 +00:00
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Answer: 204
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2017-12-12 13:48:53 +00:00
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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/about
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. http://adventofcode.com/2017/support
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. http://adventofcode.com/2017/events
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. http://adventofcode.com/2017/settings
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. http://adventofcode.com/2017/auth/logout
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. http://adventofcode.com/2017
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. http://adventofcode.com/2017
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. http://adventofcode.com/2017/leaderboard
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. http://adventofcode.com/2017/stats
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. http://adventofcode.com/2017/sponsors
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. http://adventofcode.com/2017/sponsors
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. http://adventofcode.com/2017/day/12/input
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