2024 day-2 done

2024/day-2/src/part1.rs

@@ -0,0 +1,99 @@
+#![warn(clippy::all, clippy::pedantic)]
+
+use error_stack::{Report, Result, ResultExt};
+use nom::{character::complete, multi::separated_list1, IResult};
+use std::cmp::Ordering;
+use thiserror::Error;
+
+#[derive(Debug, PartialEq, Eq)]
+enum Safety {
+    Safe,
+    UnSafe,
+}
+
+#[derive(Debug, PartialEq, Eq)]
+struct XmasReport {
+    levels: Vec<u32>,
+}
+
+impl XmasReport {
+    pub fn is_safe(&self) -> Safety {
+        let mut dir = Ordering::Equal;
+        for i in 1..self.levels.len() {
+            if !(1_u32..=3).contains(&(self.levels[i - 1].abs_diff(self.levels[i]))) {
+                return Safety::UnSafe;
+            }
+            let new_dir = self.levels[i - 1].cmp(&self.levels[i]);
+            if dir != Ordering::Equal && dir != new_dir {
+                return Safety::UnSafe;
+            }
+            dir = new_dir;
+        }
+        Safety::Safe
+    }
+}
+
+// day-2
+#[derive(Debug, Error)]
+pub enum Day2Part1Error {
+    #[error("Problem parsing Day 2")]
+    ParseError,
+}
+
+/// Day-2 Part 1 for 2024 advent of code
+/// Problem can be found here: <https://adventofcode.com/2024/day/2>
+///
+/// # Errors
+/// - `ParseError` there was an issue with the parser
+pub fn part1(input: &str) -> Result<String, Day2Part1Error> {
+    let (_, reports) = parse_input(input)
+        .map_err(|x| Report::from(x.to_owned()))
+        .change_context(Day2Part1Error::ParseError)?;
+    Ok(reports
+        .iter()
+        .filter(|x| x.is_safe() == Safety::Safe)
+        .count()
+        .to_string())
+}
+
+fn parse_level(input: &str) -> IResult<&str, XmasReport> {
+    let (input, v) = separated_list1(complete::space1, complete::u32)(input)?;
+    Ok((input, XmasReport { levels: v }))
+}
+
+fn parse_input(input: &str) -> IResult<&str, Vec<XmasReport>> {
+    separated_list1(complete::line_ending, parse_level)(input)
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use rstest::rstest;
+
+    #[rstest]
+    #[case("7 6 4 2 1", Safety::Safe)]
+    #[case("1 2 7 8 9", Safety::UnSafe)]
+    #[case("9 7 6 2 1", Safety::UnSafe)]
+    #[case("1 3 2 4 5", Safety::UnSafe)]
+    #[case("8 6 4 4 1", Safety::UnSafe)]
+    #[case("1 3 6 7 9", Safety::Safe)]
+    fn part1_report_safety(#[case] input: &str, #[case] expected: Safety) {
+        let (_, tester) = parse_level(input).expect("should be valid input");
+        assert_eq!(tester.is_safe(), expected);
+    }
+
+    const INPUT: &str = "7 6 4 2 1
+1 2 7 8 9
+9 7 6 2 1
+1 3 2 4 5
+8 6 4 4 1
+1 3 6 7 9";
+
+    #[test_log::test]
+    #[test_log(default_log_filter = "trace")]
+    fn part1_works() {
+        let result = part1(INPUT).unwrap();
+        assert_eq!(result, "2".to_string());
+    }
+}
+