81 lines
2.7 KiB
Markdown
81 lines
2.7 KiB
Markdown
|
## \-\-- Day 12: Digital Plumber \-\--
|
||
|
|
|
||
|
|
Walking along the memory banks of the stream, you find a small village
|
||
|
|
that is experiencing a little confusion: some programs can\'t
|
||
|
|
communicate with each other.
|
||
|
|
|
||
|
|
Programs in this village communicate using a fixed system of *pipes*.
|
||
|
|
Messages are passed between programs using these pipes, but most
|
||
|
|
programs aren\'t connected to each other directly. Instead, programs
|
||
|
|
pass messages between each other until the message reaches the intended
|
||
|
|
recipient.
|
||
|
|
|
||
|
|
For some reason, though, some of these messages aren\'t ever reaching
|
||
|
|
their intended recipient, and the programs suspect that some
|
||
|
|
pipes
|
||
|
|
are missing. They would like you to investigate.
|
||
|
|
|
||
|
|
You walk through the village and record the ID of each program and the
|
||
|
|
IDs with which it can communicate directly (your puzzle input). Each
|
||
|
|
program has one or more programs with which it can communicate, and
|
||
|
|
these pipes are bidirectional; if `8` says it can communicate with `11`,
|
||
|
|
then `11` will say it can communicate with `8`.
|
||
|
|
|
||
|
|
You need to figure out how many programs are in the group that contains
|
||
|
|
program ID `0`.
|
||
|
|
|
||
|
|
For example, suppose you go door-to-door like a travelling salesman and
|
||
|
|
record the following list:
|
||
|
|
|
||
|
|
0 <-> 2
|
||
|
|
1 <-> 1
|
||
|
|
2 <-> 0, 3, 4
|
||
|
|
3 <-> 2, 4
|
||
|
|
4 <-> 2, 3, 6
|
||
|
|
5 <-> 6
|
||
|
|
6 <-> 4, 5
|
||
|
|
|
||
|
|
In this example, the following programs are in the group that contains
|
||
|
|
program ID `0`:
|
||
|
|
|
||
|
|
- Program `0` by definition.
|
||
|
|
- Program `2`, directly connected to program `0`.
|
||
|
|
- Program `3` via program `2`.
|
||
|
|
- Program `4` via program `2`.
|
||
|
|
- Program `5` via programs `6`, then `4`, then `2`.
|
||
|
|
- Program `6` via programs `4`, then `2`.
|
||
|
|
|
||
|
|
Therefore, a total of `6` programs are in this group; all but program
|
||
|
|
`1`, which has a pipe that connects it to itself.
|
||
|
|
|
||
|
|
*How many programs* are in the group that contains program ID `0`?
|
||
|
|
|
||
|
|
Your puzzle answer was `113`.
|
||
|
|
|
||
|
|
## \-\-- Part Two \-\-- {#part2}
|
||
|
|
|
||
|
|
There are more programs than just the ones in the group containing
|
||
|
|
program ID `0`. The rest of them have no way of reaching that group, and
|
||
|
|
still might have no way of reaching each other.
|
||
|
|
|
||
|
|
A *group* is a collection of programs that can all communicate via pipes
|
||
|
|
either directly or indirectly. The programs you identified just a moment
|
||
|
|
ago are all part of the same group. Now, they would like you to
|
||
|
|
determine the total number of groups.
|
||
|
|
|
||
|
|
In the example above, there were `2` groups: one consisting of programs
|
||
|
|
`0,2,3,4,5,6`, and the other consisting solely of program `1`.
|
||
|
|
|
||
|
|
*How many groups are there* in total?
|
||
|
|
|
||
|
|
Your puzzle answer was `202`.
|
||
|
|
|
||
|
|
Both parts of this puzzle are complete! They provide two gold stars:
|
||
|
|
\*\*
|
||
|
|
|
||
|
|
At this point, you should [return to your Advent calendar](/2017) and
|
||
|
|
try another puzzle.
|
||
|
|
|
||
|
|
If you still want to see it, you can [get your puzzle
|
||
|
|
input](12/input).
|