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use crate::prelude::*;
pub struct Line {
c: char,
n1: usize,
n2: usize,
password: String,
}
impl Line {
fn parse(line: &str) -> Result<Self> {
let captures =
regex_captures!(r"^([0-9]+)-([0-9]+) (.): (.*)$", line)
.context("line failed to match regex")?;
let c = captures
.get(3)
.unwrap()
.as_str()
.parse()
.context("invalid policy char")?;
let n1 = captures
.get(1)
.unwrap()
.as_str()
.parse()
.context("invalid policy lower bound")?;
let n2 = captures
.get(2)
.unwrap()
.as_str()
.parse()
.context("invalid policy upper bound")?;
let password = captures.get(4).unwrap().as_str().to_string();
Ok(Self {
c,
n1,
n2,
password,
})
}
fn valid_part_1(&self) -> bool {
let count = self.password.chars().filter(|c| *c == self.c).count();
count >= self.n1 && count <= self.n2
}
fn valid_part_2(&self) -> bool {
(self.password.chars().nth(self.n1 - 1) == Some(self.c))
^ (self.password.chars().nth(self.n2 - 1) == Some(self.c))
}
}
pub fn parse(fh: File) -> Result<impl Iterator<Item = Line>> {
Ok(parse::lines(fh).map(|line| Line::parse(&line).unwrap()))
}
pub fn part1(lines: impl Iterator<Item = Line>) -> Result<i64> {
let count = lines.filter(|l| l.valid_part_1()).count();
Ok(count.try_into()?)
}
pub fn part2(lines: impl Iterator<Item = Line>) -> Result<i64> {
let count = lines.filter(|l| l.valid_part_2()).count();
Ok(count.try_into()?)
}
#[test]
fn test() {
assert_eq!(
part1(parse(parse::data(2020, 2).unwrap()).unwrap()).unwrap(),
638
);
assert_eq!(
part2(parse(parse::data(2020, 2).unwrap()).unwrap()).unwrap(),
699
);
}
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