Day 2: Rock Paper Scissors

Author: ephemient

rs/src/day2.rs

@@ -0,0 +1,62 @@
+use std::vec::Vec;
+
+fn parse<'a, I, S>(lines: I) -> Vec<(u8, u8)>
+where
+    I: IntoIterator<Item = &'a S>,
+    S: AsRef<str> + 'a,
+{
+    lines
+        .into_iter()
+        .filter_map(|line| {
+            let mut iter = line.as_ref().split_ascii_whitespace();
+            Some((
+                iter.next()?.as_bytes().first()? - 64,
+                iter.next()?.as_bytes().first()? - 87,
+            ))
+        })
+        .collect()
+}
+
+fn score(left: u8, right: u8) -> u8 {
+    (4 + right - left) % 3 * 3 + right
+}
+
+pub fn part1<'a, I, S>(lines: I) -> u32
+where
+    I: IntoIterator<Item = &'a S>,
+    S: AsRef<str> + 'a,
+{
+    parse(lines)
+        .into_iter()
+        .map(|(left, right)| score(left, right) as u32)
+        .sum()
+}
+
+pub fn part2<'a, I, S>(lines: I) -> u32
+where
+    I: IntoIterator<Item = &'a S>,
+    S: AsRef<str> + 'a,
+{
+    parse(lines)
+        .into_iter()
+        .map(|(left, right)| score(left, 1 + (left + right) % 3) as u32)
+        .sum()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use pretty_assertions::assert_eq;
+
+    static EXAMPLE: &[&str] = &["A Y", "B X", "C Z"];
+
+    #[test]
+    fn part1_examples() {
+        assert_eq!(15, part1(EXAMPLE));
+    }
+
+    #[test]
+    fn part2_examples() {
+        assert_eq!(12, part2(EXAMPLE));
+    }
+}

rs/src/lib.rs

@@ -1 +1,2 @@
 pub mod day1;
+pub mod day2;

rs/src/main.rs

@@ -1,7 +1,7 @@
 #[macro_use]
 extern crate build_const;
 
-use aoc2022::day1;
+use aoc2022::{day1, day2};
 use std::collections::HashSet;
 use std::env;
 use std::io;
@@ -21,5 +21,12 @@ fn main() -> io::Result<()> {
         println!();
     }
 
+    if args.is_empty() || args.contains(&2) {
+        println!("Day 2");
+        println!("{:?}", day2::part1(DAY2));
+        println!("{:?}", day2::part2(DAY2));
+        println!();
+    }
+
     Ok(())
 }