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use {
anyhow::{
anyhow,
Context,
Result,
},
regex::Regex,
std::{
env::args,
fmt,
fs::File,
io::{
BufRead,
BufReader,
},
path::Path,
},
};
struct SectionAssignment {
start: usize,
end: usize,
}
impl SectionAssignment {
fn new(start: usize, end: usize) -> Self {
Self {
start,
end,
}
}
fn contains(&self, other: &SectionAssignment) -> bool {
self.start <= other.start && self.end >= other.end
}
fn overlaps(&self, other: &SectionAssignment) -> bool {
(self.start >= other.start && self.start <= other.end) ||
(self.end >= other.start && self.end <= other.end) ||
(other.start >= self.start && other.start <= self.end) ||
(other.end >= self.start && other.end <= self.end)
}
}
impl fmt::Debug for SectionAssignment {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
(0..=9).map(|i| if i >= self.start && i <= self.end {
write!(f, "{i}")
} else {
write!(f, ".")
}).last();
write!(f, " {}-{}", self.start, self.end)?;
Ok(())
}
}
type AssignmentPair = [SectionAssignment; 2];
fn read_input<T: AsRef<Path>>(filename: T) -> Result<Vec<AssignmentPair>> {
let reader = BufReader::new(File::open(filename)?);
let re = Regex::new(r"(?P<s0>[0-9]+)-(?P<e0>[0-9]+),(?P<s1>[0-9]+)-(?P<e1>[0-9]+)")
.context("Regex compilation failed.")?;
reader.lines().map(
|v| {
let s = v?;
let caps = re.captures(&s).ok_or_else(|| anyhow!("Regex matching failed."))?;
match (caps.name("s0"), caps.name("e0"), caps.name("s1"), caps.name("e1")) {
( Some(s0), Some(e0), Some(s1), Some(e1) ) => Ok([
SectionAssignment::new(s0.as_str().parse()?, e0.as_str().parse()?),
SectionAssignment::new(s1.as_str().parse()?, e1.as_str().parse()?),
]),
_ => Err(anyhow!("Parse error.")),
}
}
).collect()
}
fn part1(input: &[AssignmentPair]) -> Result<usize> {
Ok(input.iter().filter(|pair|
pair[0].contains(&pair[1]) ||
pair[1].contains(&pair[0])).count())
}
fn part2(input: &[AssignmentPair]) -> Result<usize> {
Ok(input.iter().filter(|pair| pair[0].overlaps(&pair[1])).count())
}
fn main() -> Result<()> {
let ( do_part_1, do_part_2 ) = aoc::do_parts();
let filename = args().nth(1).ok_or_else(|| anyhow!("Missing input filename"))?;
let input = read_input(filename).context("Could not read input")?;
if do_part_1 {
let solution = part1(&input).context("No solution for part 1")?;
println!("Part1, solution found to be: {}", solution);
}
if do_part_2 {
let solution = part2(&input).context("No solution for part 2")?;
println!("Part2, solution found to be: {}", solution);
}
Ok(())
}
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