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use std::ops::Range;
use anyhow::Result;
pub fn parse_range(section: &str) -> Result<Range<usize>> {
let (start, end) = section.split_once('-').unwrap();
let start = start.parse::<usize>()?;
let end = end.parse::<usize>()?;
Ok(Range { start, end })
}
fn parse_pair(input: &str) -> Result<(Range<usize>, Range<usize>)> {
let (section_a, section_b) = input.split_once(',').unwrap();
Ok((parse_range(section_a)?, parse_range(section_b)?))
}
fn range_is_subset((a, b): &(Range<usize>, Range<usize>)) -> bool {
(a.start <= b.start && a.end >= b.end) || (b.start <= a.start && b.end >= a.end)
}
fn range_is_union((a, b): &(Range<usize>, Range<usize>)) -> bool {
(a.start <= b.start && a.end >= b.start) || (b.start <= a.start && b.end >= a.start)
}
pub fn solve() -> Result<()> {
let input = include_str!("../input/day_4.txt");
println!("day 4");
println!("part 1: {}", part_1(input)?);
println!("part 2: {}", part_2(input)?);
Ok(())
}
pub fn part_1(input: &str) -> Result<usize> {
let ranges: Vec<_> = input.lines().map(parse_pair).collect::<Result<_>>()?;
Ok(ranges.into_iter().filter(range_is_subset).count())
}
pub fn part_2(input: &str) -> Result<usize> {
let ranges: Vec<_> = input.lines().map(parse_pair).collect::<Result<_>>()?;
Ok(ranges.into_iter().filter(range_is_union).count())
}
#[cfg(test)]
mod tests {
use super::*;
const TEST_INPUT: &str = r#"2-4,6-8
2-3,4-5
5-7,7-9
2-8,3-7
6-6,4-6
2-6,4-8"#;
#[test]
fn test_part_1_example() -> Result<()> {
assert_eq!(2, part_1(TEST_INPUT)?);
Ok(())
}
#[test]
fn test_part_2_example() -> Result<()> {
assert_eq!(4, part_2(TEST_INPUT)?);
Ok(())
}
}
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