2024 day-1 done

2024/day-1/src/part1.rs

@@ -0,0 +1,54 @@
+#![warn(clippy::all, clippy::pedantic)]
+
+use error_stack::Result;
+use nom::{character::complete, multi::separated_list1, sequence::separated_pair, IResult};
+use thiserror::Error;
+
+// day-1
+#[derive(Debug, Error)]
+pub enum Day1Part1Error {
+    #[error("Problem parsing Day 1")]
+    ParseError,
+}
+
+pub fn part1(input: &str) -> Result<u64, Day1Part1Error> {
+    let (_, (mut col1, mut col2)) =
+        parse_input(input).expect("there should always be valid input from aoc");
+    col1.sort();
+    col2.sort();
+
+    Ok(col1
+        .into_iter()
+        .zip(col2.iter())
+        .map(|(a, b)| u64::max(a, *b) - u64::min(a, *b))
+        .sum())
+}
+
+fn parse_input(input: &str) -> IResult<&str, (Vec<u64>, Vec<u64>)> {
+    let (input, combo) = separated_list1(
+        complete::line_ending,
+        separated_pair(complete::u64, complete::space1, complete::u64),
+    )(input)?;
+    Ok((input, combo.into_iter().unzip()))
+
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    const INPUT: &str = "3   4
+4   3
+2   5
+1   3
+3   9
+3   3 ";
+
+    #[test_log::test]
+    #[test_log(default_log_filter = "trace")]
+    fn part1_works() {
+        let result = part1(INPUT).unwrap();
+        assert_eq!(result, 11);
+    }
+}
+