day 4

Cargo.lock

@@ -5,3 +5,28 @@ version = 3
 [[package]]
 name = "aoc2022"
 version = "0.1.0"
+dependencies = [
+ "nom",
+]
+
+[[package]]
+name = "memchr"
+version = "2.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2dffe52ecf27772e601905b7522cb4ef790d2cc203488bbd0e2fe85fcb74566d"
+
+[[package]]
+name = "minimal-lexical"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "68354c5c6bd36d73ff3feceb05efa59b6acb7626617f4962be322a825e61f79a"
+
+[[package]]
+name = "nom"
+version = "7.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a8903e5a29a317527874d0402f867152a3d21c908bb0b933e416c65e301d4c36"
+dependencies = [
+ "memchr",
+ "minimal-lexical",
+]

Cargo.toml

@@ -6,3 +6,4 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+nom = "7.1.1"

src/bin/day04_1.rs

@@ -0,0 +1,7 @@
+use aoc2022::day04::process_part_1;
+use std::fs;
+
+fn main() {
+    let file = fs::read_to_string("./inputs/day4.txt").unwrap();
+    println!("{}", process_part_1(&file));
+}

src/bin/day04_2.rs

@@ -0,0 +1,7 @@
+use aoc2022::day04::process_part_2;
+use std::fs;
+
+fn main() {
+    let file = fs::read_to_string("./inputs/day4.txt").unwrap();
+    println!("{}", process_part_2(&file));
+}

src/day04.rs

@@ -0,0 +1,74 @@
+use nom::IResult;
+use std::ops::RangeInclusive;
+
+pub fn process_part_1(input: &str) -> usize {
+    let (_, assignments) = section_assignments(input).unwrap();
+    assignments
+        .iter()
+        .filter(|(a, b)| range_contains(a, b) || range_contains(b, a))
+        .count()
+}
+
+pub fn process_part_2(input: &str) -> usize {
+    let (_, assignments) = section_assignments(input).unwrap();
+    assignments
+        .iter()
+        .filter(|(a, b)| a.clone().into_iter().any(|n| b.contains(&n)))
+        .count()
+}
+
+fn range_contains(haystack: &RangeInclusive<u32>, needle: &RangeInclusive<u32>) -> bool {
+    haystack.contains(needle.start()) && haystack.contains(needle.end())
+}
+
+fn section_assignments(
+    input: &str,
+) -> IResult<&str, Vec<(RangeInclusive<u32>, RangeInclusive<u32>)>> {
+    use nom::character::complete::newline;
+    use nom::multi::separated_list1;
+
+    let (input, ranges) = separated_list1(newline, line)(input)?;
+    Ok((input, ranges))
+}
+
+fn line(input: &str) -> IResult<&str, (RangeInclusive<u32>, RangeInclusive<u32>)> {
+    use nom::bytes::complete::tag;
+
+    let (input, start) = sections(input)?;
+    let (input, _) = tag(",")(input)?;
+    let (input, end) = sections(input)?;
+    Ok((input, (start, end)))
+}
+
+fn sections(input: &str) -> IResult<&str, RangeInclusive<u32>> {
+    use nom::bytes::complete::tag;
+    use nom::character::complete;
+
+    let (input, start) = complete::u32(input)?;
+    let (input, _) = tag("-")(input)?;
+    let (input, end) = complete::u32(input)?;
+
+    Ok((input, start..=end))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const INPUT: &str = "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 day1() {
+        assert_eq!(process_part_1(INPUT), 2);
+    }
+
+    #[test]
+    fn day2() {
+        assert_eq!(process_part_2(INPUT), 4);
+    }
+}

src/lib.rs

@@ -4,3 +4,4 @@ extern crate core;
 pub mod day01;
 pub mod day02;
 pub mod day03;
+pub mod day04;