Problem Day 8: Haunted Wasteland
Here the day 8 problem statement: https://adventofcode.com/2023/day/8
Solution Part 1
pub fn part_one(input: &str) -> Option<u32> {
let commands = input.lines().next().unwrap();
let mut network: HashMap<&str, (&str, &str)> = HashMap::new();
input.lines().skip(2).for_each(|line| {
let parts: Vec<&str> = line.split(" = ").collect();
let key = parts[0];
let value = parts[1]
.strip_prefix('(')
.unwrap()
.strip_suffix(')')
.unwrap()
.split_once(", ")
.unwrap();
network.insert(key, value);
});
let mut step = network.get("AAA").unwrap();
let mut counter = 0;
for command in commands.chars().cycle() {
counter += 1;
if command == 'L' {
if step.0 == "ZZZ" {
return Some(counter);
}
let next = network.get(step.0).unwrap();
step = next;
} else if command == 'R' {
if step.1 == "ZZZ" {
return Some(counter);
}
let next = network.get(step.1).unwrap();
step = next;
}
}
Some(counter)
}
Solution Part 2
fn lcm(nums: &[usize]) -> usize {
let mut result = 1;
for &num in nums {
result = num * result / gcd(num, result);
}
result
}
fn gcd(a: usize, b: usize) -> usize {
if b == 0 {
return a;
}
gcd(b, a % b)
}
pub fn part_two(input: &str) -> Option<usize> {
let commands = input.lines().next().unwrap();
let mut network: HashMap<&str, (&str, &str)> = HashMap::new();
input.lines().skip(2).for_each(|line| {
let parts: Vec<&str> = line.split(" = ").collect();
let key = parts[0];
let value = parts[1]
.strip_prefix('(')
.unwrap()
.strip_suffix(')')
.unwrap()
.split_once(", ")
.unwrap();
network.insert(key, value);
});
let start_nodes: Vec<_> = network.iter().filter(|x| x.0.ends_with('A')).collect();
let mut end_counts = HashMap::<&str, usize>::new();
for start in start_nodes.iter() {
let mut current_node_name = *start.0;
let mut count = 0;
let mut commands_list = commands.chars().cycle();
while !current_node_name.ends_with('Z') {
let command = commands_list.next().unwrap();
let current_node = network.get(current_node_name).unwrap();
let next_node_name = match command {
'L' => current_node.0,
'R' => current_node.1,
_ => unreachable!(),
};
current_node_name = next_node_name;
count += 1;
}
end_counts.insert(start.0, count);
}
let counts = end_counts.values().cloned().collect::<Vec<_>>();
let lcm = lcm(&counts);
Some(lcm)
}
Here the repository with all puzzle solutions.
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