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use crate::{Problem, Solution};
pub struct Day12;
impl Problem for Day12 {
const DAY: u8 = 12;
const INPUT: &'static str = include_str!("../input/day_12.txt");
}
impl Solution for Day12 {
type Answer1 = usize;
type Answer2 = usize;
fn part_1(input: &str) -> anyhow::Result<Self::Answer1> {
Ok(input
.lines()
.map(std::str::FromStr::from_str)
.try_collect::<Vec<Row<1>>>()?
.into_iter()
.map(Row::solve)
.sum())
}
fn part_2(input: &str) -> anyhow::Result<Self::Answer2> {
Ok(input
.lines()
.map(std::str::FromStr::from_str)
.try_collect::<Vec<Row<5>>>()?
.into_iter()
.map(Row::solve)
.sum())
}
}
#[derive(Debug, Default, Clone, PartialEq, Eq, PartialOrd, Ord)]
struct Row<const REP: u8> {
states: Vec<State>,
groups: Vec<usize>,
}
impl<const REP: u8> Row<REP> {
fn new(states: Vec<State>, groups: Vec<usize>) -> Self {
let states = std::iter::repeat(states)
.take(REP as usize)
.intersperse(vec![State::Unknown])
.flatten()
.collect::<Vec<_>>();
let groups = std::iter::repeat(groups)
.take(REP as usize)
.flatten()
.collect::<Vec<_>>();
Self { states, groups }
}
fn solve(mut self) -> usize {
self.states.push(State::Good);
let mut groups = vec![Group::default()];
for state in self.states.into_iter() {
let mut next_groups = Vec::new();
for Group {
seq,
index,
count,
prev,
} in groups
{
if state == State::Unknown || state == State::Bad {
next_groups.push(Group {
seq: seq + 1,
index,
count,
prev: Some(State::Bad),
})
}
if state == State::Unknown || state == State::Good {
if prev != Some(State::Bad) {
next_groups.push(Group {
seq: 0,
index,
count,
prev: Some(State::Good),
});
} else if self.groups.get(index).is_some_and(|s| *s == seq) {
next_groups.push(Group {
seq: 0,
index: index + 1,
count,
prev: Some(State::Good),
});
}
}
}
next_groups.sort();
groups = next_groups.into_iter().fold(Vec::new(), |mut acc, group| {
if let Some(last) = acc.last_mut() {
if last.seq == group.seq && last.index == group.index && last.prev == group.prev
{
last.count += group.count;
return acc;
}
}
acc.push(group);
acc
});
}
groups
.into_iter()
.filter_map(|g| (g.index == self.groups.len()).then_some(g.count))
.sum()
}
}
impl<const REP: u8> std::str::FromStr for Row<REP> {
type Err = anyhow::Error;
fn from_str(s: &str) -> Result<Self, Self::Err> {
let (states, groups) = s.split_once(' ').unwrap();
let states = states
.chars()
.map(TryFrom::try_from)
.try_collect::<Vec<State>>()?;
let groups = groups
.split(',')
.map(std::str::FromStr::from_str)
.try_collect::<Vec<usize>>()?;
Ok(Self::new(states, groups))
}
}
impl<const REP: u8> std::fmt::Display for Row<REP> {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
self.states
.iter()
.try_for_each(|s| write!(f, "{}", char::from(*s)))?;
self.groups.iter().enumerate().try_for_each(|(i, n)| {
if i == 0 {
write!(f, " {n}")
} else {
write!(f, ",{n}")
}
})
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
struct Group {
seq: usize,
index: usize,
count: usize,
prev: Option<State>,
}
impl Default for Group {
fn default() -> Self {
Self {
seq: 0,
index: 0,
count: 1,
prev: None,
}
}
}
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
enum State {
Good,
Bad,
Unknown,
}
impl TryFrom<char> for State {
type Error = anyhow::Error;
fn try_from(value: char) -> Result<Self, Self::Error> {
match value {
'.' => Ok(State::Good),
'#' => Ok(State::Bad),
'?' => Ok(State::Unknown),
c => Err(anyhow::format_err!("Unknown spring condition: {c}")),
}
}
}
impl From<State> for char {
fn from(value: State) -> Self {
match value {
State::Good => '.',
State::Bad => '#',
State::Unknown => '?',
}
}
}
#[cfg(test)]
mod tests {
use super::*;
const INPUT: &str = indoc::indoc! {"
???.### 1,1,3
.??..??...?##. 1,1,3
?#?#?#?#?#?#?#? 1,3,1,6
????.#...#... 4,1,1
????.######..#####. 1,6,5
?###???????? 3,2,1
"};
#[test]
fn test_part_1() -> anyhow::Result<()> {
Ok(assert_eq!(21, Day12::part_1(INPUT)?))
}
#[test]
fn test_part_2() -> anyhow::Result<()> {
Ok(assert_eq!(525152, Day12::part_2(INPUT)?))
}
}
|
