103 lines
2.4 KiB
Rust
103 lines
2.4 KiB
Rust
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use std::str::FromStr;
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const DATA: &'static str = include_str!("../data/day3.txt");
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// const DATA: &'static str = "
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// vJrwpWtwJgWrhcsFMMfFFhFp
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// jqHRNqRjqzjGDLGLrsFMfFZSrLrFZsSL
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// PmmdzqPrVvPwwTWBwg
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// wMqvLMZHhHMvwLHjbvcjnnSBnvTQFn
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// ttgJtRGJQctTZtZT
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// CrZsJsPPZsGzwwsLwLmpwMDw
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// ";
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#[derive(Debug)]
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enum DataError {
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Imbalanced,
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UnknownValue,
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NoDuplicate,
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NoTriplicate,
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ShortGroup,
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}
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struct Rucksack {
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left: Vec<u8>,
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right: Vec<u8>,
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}
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impl Rucksack {
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fn find_duplicate(&self) -> Option<u8> {
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// pretty sure this is faster than hash set, given the sizes involved
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self.left.iter()
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.find(|c| self.right.contains(c))
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.map(|c| *c)
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}
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fn iter_all(&self) -> impl Iterator<Item = &u8> {
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self.left.iter().chain(self.right.iter())
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}
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fn contains(&self, v: u8) -> bool {
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self.left.contains(&v) || self.right.contains(&v)
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}
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}
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impl FromStr for Rucksack {
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type Err = DataError;
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fn from_str(line: &str) -> Result<Rucksack, DataError> {
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let line = line.trim();
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if line.len() % 2 != 0 {
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return Err(DataError::Imbalanced);
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}
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let (a, b) = line.as_bytes().split_at(line.len() / 2);
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Ok(Rucksack {
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left: a.into(),
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right: b.into(),
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})
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}
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}
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fn priority(c: u8) -> Result<u64, DataError> {
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match c {
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// lowercase
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97..=122 => Ok(c as u64 - 96),
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// uppercase
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65..=90 => Ok(c as u64 - 38),
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_ => Err(DataError::UnknownValue),
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}
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}
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fn main() -> Result<(), DataError> {
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let mut dup_total = 0;
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let rucks = DATA.trim()
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.split("\n")
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.map(|line| Rucksack::from_str(line))
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.collect::<Result<Vec<Rucksack>, DataError>>()?;
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for ruck in rucks.iter() {
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let dup = ruck.find_duplicate()
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.ok_or(DataError::NoDuplicate)?;
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dup_total += priority(dup)?;
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}
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println!("Part 1: {dup_total}");
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let mut groups_total = 0;
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for (idx, ruck) in rucks.iter().enumerate().step_by(3) {
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if idx > rucks.len() - 3 {
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return Err(DataError::ShortGroup);
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}
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let badge = *ruck.iter_all()
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.find(|&v| rucks[idx + 1].contains(*v) && rucks[idx + 2].contains(*v))
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.ok_or(DataError::NoTriplicate)?;
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groups_total += priority(badge)?;
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}
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println!("Part 2: {groups_total}");
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Ok(())
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}
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