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use std::{cmp::Ordering, collections::HashMap, ops::ControlFlow, str::FromStr};
use crate::{Problem, Solution};
pub struct Day19;
impl Problem for Day19 {
const DAY: u8 = 19;
const INPUT: &'static str = include_str!("../input/day_19.txt");
}
impl Solution for Day19 {
type Answer1 = usize;
type Answer2 = usize;
fn part_1(input: &str) -> anyhow::Result<Self::Answer1> {
let (workflows, parts) = input.split_once("\n\n").unwrap();
let workflows = workflows
.lines()
.map(parse_workflow)
.try_collect::<HashMap<[char; 3], Workflow>>()
.unwrap();
let parts = parts
.lines()
.map(parse_part)
.try_collect::<Vec<[usize; 4]>>()?;
let mut next = ['i', 'n', ' '];
let mut sum = 0;
for part in parts {
while let Some(workflow) = workflows.get(&next) {
if let ControlFlow::Continue(n) = workflow.process_part(&part) {
next = n
} else {
sum += part.iter().sum::<usize>()
}
}
}
Ok(sum)
}
fn part_2(input: &str) -> anyhow::Result<Self::Answer2> {
todo!()
}
}
fn parse_workflow(s: &str) -> anyhow::Result<([char; 3], Workflow)> {
let (name, rules) = s
.split_once('{')
.ok_or_else(|| anyhow::format_err!("Failed to parse workflow: {s}"))?;
let mut iter = name.chars();
let name = [
iter.next().unwrap(),
iter.next().unwrap_or(' '),
iter.next().unwrap_or(' '),
];
Ok((name, rules.trim_end_matches('}').parse()?))
}
fn parse_part(s: &str) -> anyhow::Result<[usize; 4]> {
s.strip_prefix('{')
.and_then(|s| s.strip_suffix('}'))
.ok_or(anyhow::format_err!("Invalid part format: {s}"))?
.split(',')
.map(|s| s.trim_start_matches(['x', 'm', 'a', 's', '=']).parse())
.try_collect::<Vec<usize>>()?
.try_into()
.map_err(|_| anyhow::format_err!("Failed to parse part: {s}"))
}
fn parse_output(s: &str) -> anyhow::Result<Output> {
Ok(match s {
"A" => ControlFlow::Break(true),
"R" => ControlFlow::Break(false),
w if (2..=3).contains(&w.len()) => {
let mut iter = w.chars();
ControlFlow::Continue([
iter.next().unwrap(),
iter.next().unwrap_or(' '),
iter.next().unwrap_or(' '),
])
}
e => Err(anyhow::format_err!("Invalid output value: {e}"))?,
})
}
type Part = [usize; 4];
type Label = [char; 3];
type Output = ControlFlow<bool, Label>;
struct Workflow {
rules: Vec<Rule>,
last: ControlFlow<bool, Label>,
}
impl Workflow {
fn process_part(&self, part: &Part) -> ControlFlow<bool, Label> {
self.rules
.iter()
.find_map(|r| r.process_part(part))
.unwrap_or(self.last)
}
}
impl FromStr for Workflow {
type Err = anyhow::Error;
fn from_str(s: &str) -> Result<Self, Self::Err> {
let mut iter = s.split(',');
let last = iter
.next_back()
.ok_or_else(|| anyhow::format_err!("Workflow contains no rules: {s}"))
.and_then(parse_output)?;
let rules = iter.map(|s| s.parse()).try_collect::<Vec<Rule>>()?;
Ok(Self { rules, last })
}
}
struct Rule {
field: u8,
cmp: Ordering,
value: usize,
output: ControlFlow<bool, Label>,
}
impl Rule {
fn process_part(&self, part: &[usize; 4]) -> Option<ControlFlow<bool, Label>> {
(self.value.cmp(&part[self.field as usize]) == self.cmp).then_some(self.output)
}
}
impl FromStr for Rule {
type Err = anyhow::Error;
fn from_str(s: &str) -> Result<Self, Self::Err> {
let (cond, output) = s
.split_once(':')
.ok_or_else(|| anyhow::format_err!("Failed to parse rule: {s}"))?;
let mut iter = cond.chars();
let field = match iter.next() {
Some('x') => 0,
Some('m') => 1,
Some('a') => 2,
Some('s') => 3,
f => anyhow::bail!("Failed to parse rule field: {f:?}"),
};
let cmp = match iter.next() {
Some('<') => Ordering::Less,
Some('=') => Ordering::Equal,
Some('>') => Ordering::Greater,
c => Err(anyhow::format_err!("Failed to parse comparison: {c:?}"))?,
};
let value = iter.collect::<String>().parse()?;
Ok(Self {
field,
cmp,
value,
output: parse_output(output)?,
})
}
}
#[repr(u8)]
enum Catagory {
X,
M,
A,
S,
}
impl FromStr for Catagory {
type Err = anyhow::Error;
fn from_str(s: &str) -> Result<Self, Self::Err> {
Ok(match s {
"x" => Self::X,
"m" => Self::M,
"a" => Self::A,
"s" => Self::S,
s => anyhow::bail!("Failed to parse field: {s}"),
})
}
}
#[cfg(test)]
mod tests {
use super::*;
const INPUT: &str = indoc::indoc! {r#"
px{a<2006:qkq,m>2090:A,rfg}
pv{a>1716:R,A}
lnx{m>1548:A,A}
rfg{s<537:gd,x>2440:R,A}
qs{s>3448:A,lnx}
qkq{x<1416:A,crn}
crn{x>2662:A,R}
in{s<1351:px,qqz}
qqz{s>2770:qs,m<1801:hdj,R}
gd{a>3333:R,R}
hdj{m>838:A,pv}
{x=787,m=2655,a=1222,s=2876}
{x=1679,m=44,a=2067,s=496}
{x=2036,m=264,a=79,s=2244}
{x=2461,m=1339,a=466,s=291}
{x=2127,m=1623,a=2188,s=1013}
"#};
#[test]
fn test_part_1() -> anyhow::Result<()> {
Ok(assert_eq!(19114, Day19::part_1(INPUT)?))
}
}
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