264 lines
7.9 KiB
Plaintext
264 lines
7.9 KiB
Plaintext
Advent of Code
|
||
|
||
--- Day 22: Sporifica Virus ---
|
||
|
||
Diagnostics indicate that the local grid computing cluster has been
|
||
contaminated with the Sporifica Virus. The grid computing cluster is a
|
||
seemingly-infinite two-dimensional grid of compute nodes. Each node is either
|
||
clean or infected by the virus.
|
||
|
||
To prevent overloading the nodes (which would render them useless to the
|
||
virus) or detection by system administrators, exactly one virus carrier moves
|
||
through the network, infecting or cleaning nodes as it moves. The virus
|
||
carrier is always located on a single node in the network (the current node)
|
||
and keeps track of the direction it is facing.
|
||
|
||
To avoid detection, the virus carrier works in bursts; in each burst, it
|
||
wakes up, does some work, and goes back to sleep. The following steps are all
|
||
executed in order one time each burst:
|
||
|
||
* If the current node is infected, it turns to its right. Otherwise, it
|
||
turns to its left. (Turning is done in-place; the current node does not
|
||
change.)
|
||
* If the current node is clean, it becomes infected. Otherwise, it becomes
|
||
cleaned. (This is done after the node is considered for the purposes of
|
||
changing direction.)
|
||
* The virus carrier moves forward one node in the direction it is facing.
|
||
|
||
Diagnostics have also provided a map of the node infection status (your
|
||
puzzle input). Clean nodes are shown as .; infected nodes are shown as #.
|
||
This map only shows the center of the grid; there are many more nodes beyond
|
||
those shown, but none of them are currently infected.
|
||
|
||
The virus carrier begins in the middle of the map facing up.
|
||
|
||
For example, suppose you are given a map like this:
|
||
|
||
..#
|
||
#..
|
||
...
|
||
|
||
Then, the middle of the infinite grid looks like this, with the virus
|
||
carrier's position marked with [ ]:
|
||
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . # . . .
|
||
. . . #[.]. . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
|
||
The virus carrier is on a clean node, so it turns left, infects the node, and
|
||
moves left:
|
||
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . # . . .
|
||
. . .[#]# . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
|
||
The virus carrier is on an infected node, so it turns right, cleans the node,
|
||
and moves up:
|
||
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . .[.]. # . . .
|
||
. . . . # . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
|
||
Four times in a row, the virus carrier finds a clean, infects it, turns left,
|
||
and moves forward, ending in the same place and still facing up:
|
||
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . #[#]. # . . .
|
||
. . # # # . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
|
||
Now on the same node as before, it sees an infection, which causes it to turn
|
||
right, clean the node, and move forward:
|
||
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . # .[.]# . . .
|
||
. . # # # . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
|
||
After the above actions, a total of 7 bursts of activity had taken place. Of
|
||
them, 5 bursts of activity caused an infection.
|
||
|
||
After a total of 70, the grid looks like this, with the virus carrier facing
|
||
up:
|
||
|
||
. . . . . # # . .
|
||
. . . . # . . # .
|
||
. . . # . . . . #
|
||
. . # . #[.]. . #
|
||
. . # . # . . # .
|
||
. . . . . # # . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
|
||
By this time, 41 bursts of activity caused an infection (though most of those
|
||
nodes have since been cleaned).
|
||
|
||
After a total of 10000 bursts of activity, 5587 bursts will have caused an
|
||
infection.
|
||
|
||
Given your actual map, after 10000 bursts of activity, how many bursts cause
|
||
a node to become infected? (Do not count nodes that begin infected.)
|
||
|
||
Your puzzle answer was _______.
|
||
|
||
The first half of this puzzle is complete! It provides one gold star: *
|
||
|
||
--- Part Two ---
|
||
|
||
As you go to remove the virus from the infected nodes, it evolves to resist
|
||
your attempt.
|
||
|
||
Now, before it infects a clean node, it will weaken it to disable your
|
||
defenses. If it encounters an infected node, it will instead flag the node to
|
||
be cleaned in the future. So:
|
||
|
||
* Clean nodes become weakened.
|
||
* Weakened nodes become infected.
|
||
* Infected nodes become flagged.
|
||
* Flagged nodes become clean.
|
||
|
||
Every node is always in exactly one of the above states.
|
||
|
||
The virus carrier still functions in a similar way, but now uses the
|
||
following logic during its bursts of action:
|
||
|
||
* Decide which way to turn based on the current node:
|
||
|
||
* If it is clean, it turns left.
|
||
* If it is weakened, it does not turn, and will continue moving in the
|
||
same direction.
|
||
* If it is infected, it turns right.
|
||
* If it is flagged, it reverses direction, and will go back the way it
|
||
came.
|
||
|
||
* Modify the state of the current node, as described above.
|
||
* The virus carrier moves forward one node in the direction it is facing.
|
||
|
||
Start with the same map (still using . for clean and # for infected) and
|
||
still with the virus carrier starting in the middle and facing up.
|
||
|
||
Using the same initial state as the previous example, and drawing weakened as
|
||
W and flagged as F, the middle of the infinite grid looks like this, with the
|
||
virus carrier's position again marked with [ ]:
|
||
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . # . . .
|
||
. . . #[.]. . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
|
||
This is the same as before, since no initial nodes are weakened or flagged.
|
||
The virus carrier is on a clean node, so it still turns left, instead weakens
|
||
the node, and moves left:
|
||
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . # . . .
|
||
. . .[#]W . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
|
||
The virus carrier is on an infected node, so it still turns right, instead
|
||
flags the node, and moves up:
|
||
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . .[.]. # . . .
|
||
. . . F W . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
|
||
This process repeats three more times, ending on the previously-flagged node
|
||
and facing right:
|
||
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . W W . # . . .
|
||
. . W[F]W . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
|
||
Finding a flagged node, it reverses direction and cleans the node:
|
||
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . W W . # . . .
|
||
. .[W]. W . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
|
||
The weakened node becomes infected, and it continues in the same direction:
|
||
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . W W . # . . .
|
||
.[.]# . W . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
. . . . . . . . .
|
||
|
||
Of the first 100 bursts, 26 will result in infection. Unfortunately, another
|
||
feature of this evolved virus is speed; of the first 10000000 bursts, 2511944
|
||
will result in infection.
|
||
|
||
Given your actual map, after 10000000 bursts of activity, how many bursts
|
||
cause a node to become infected? (Do not count nodes that begin infected.)
|
||
|
||
Although it hasn't changed, you can still get your puzzle input.
|
||
|
||
Answer: _____________________ [ [Submit] ]
|
||
|
||
References
|
||
|
||
Visible links
|
||
. http://adventofcode.com/
|
||
. http://adventofcode.com/2017/about
|
||
. http://adventofcode.com/2017/support
|
||
. http://adventofcode.com/2017/events
|
||
. http://adventofcode.com/2017/settings
|
||
. http://adventofcode.com/2017/auth/logout
|
||
. http://adventofcode.com/2017
|
||
. http://adventofcode.com/2017
|
||
. http://adventofcode.com/2017/leaderboard
|
||
. http://adventofcode.com/2017/stats
|
||
. http://adventofcode.com/2017/sponsors
|
||
. http://adventofcode.com/2017/sponsors
|
||
. https://en.wikipedia.org/wiki/Morris_worm#The_mistake
|
||
. https://www.youtube.com/watch?v=2vj37yeQQHg
|
||
. http://adventofcode.com/2017/day/22/input
|