--- Day 8: Haunted Wasteland ---
You're still riding a camel across Desert Island when you spot a sandstorm quickly approaching. When you turn to warn the Elf, she disappears before your eyes! To be fair, she had just finished warning you about ghosts a few minutes ago.
One of the camel's pouches is labeled "maps" - sure enough, it's full of documents (your puzzle input) about how to navigate the desert. At least, you're pretty sure that's what they are; one of the documents contains a list of left/right instructions, and the rest of the documents seem to describe some kind of network of labeled nodes.
It seems like you're meant to use the left/right instructions to navigate the network. Perhaps if you have the camel follow the same instructions, you can escape the haunted wasteland!
After examining the maps for a bit, two nodes stick out: AAA
and ZZZ
. You feel like AAA
is where you are now, and you have to follow the left/right instructions until you reach ZZZ
.
This format defines each node of the network individually. For example:
RL
AAA = (BBB, CCC)
BBB = (DDD, EEE)
CCC = (ZZZ, GGG)
DDD = (DDD, DDD)
EEE = (EEE, EEE)
GGG = (GGG, GGG)
ZZZ = (ZZZ, ZZZ)
Starting with AAA
, you need to look up the next element based on the next left/right instruction in your input. In this example, start with AAA
and go right (R
) by choosing the right element of AAA
, CCC
. Then, L
means to choose the left element of CCC
, ZZZ
. By following the left/right instructions, you reach ZZZ
in 2
steps.
Of course, you might not find ZZZ
right away. If you run out of left/right instructions, repeat the whole sequence of instructions as necessary: RL
really means RLRLRLRLRLRLRLRL...
and so on. For example, here is a situation that takes 6
steps to reach ZZZ
:
LLR
AAA = (BBB, BBB)
BBB = (AAA, ZZZ)
ZZZ = (ZZZ, ZZZ)
Starting at AAA
, follow the left/right instructions. How many steps are required to reach ZZZ
?