[rs] Solve 2022_02 part 1

rs/src/main.rs

@@ -38,6 +38,7 @@ impl Day {
 
 days! {
     Y2022D01: "2022_01",
+    Y2022D02: "2022_02",
 }
 
 #[derive(Parser)]
@@ -71,6 +72,7 @@ fn main() -> anyhow::Result<()> {
         let input = fs::read_to_string(file)?;
         match day {
             Day::Y2022D01 => y2022::d01::solve(input)?,
+            Day::Y2022D02 => y2022::d02::solve(input)?,
         }
     }
 

rs/src/y2022.rs

@@ -1 +1,2 @@
 pub mod d01;
+pub mod d02;

rs/src/y2022/d02.rs

@@ -0,0 +1,55 @@
+#[derive(Clone, Copy, PartialEq, Eq)]
+enum Choice {
+    Rock,
+    Paper,
+    Scissors,
+}
+
+impl Choice {
+    fn score_against(self, other: Self) -> u32 {
+        use self::Choice::*;
+
+        (match self {
+            Rock => 1,
+            Paper => 2,
+            Scissors => 3,
+        } + match (self, other) {
+            (Rock, Paper) | (Paper, Scissors) | (Scissors, Rock) => 0,
+            (Rock, Rock) | (Paper, Paper) | (Scissors, Scissors) => 3,
+            (Rock, Scissors) | (Paper, Rock) | (Scissors, Paper) => 6,
+        })
+    }
+}
+
+fn read_round(line: &str) -> (Choice, Choice) {
+    let elems = line.split(' ').take(2).collect::<Vec<_>>();
+    let l = match elems[0] {
+        "A" => Choice::Rock,
+        "B" => Choice::Paper,
+        "C" => Choice::Scissors,
+        _ => panic!(),
+    };
+    let r = match elems[1] {
+        "X" => Choice::Rock,
+        "Y" => Choice::Paper,
+        "Z" => Choice::Scissors,
+        _ => panic!(),
+    };
+    (l, r)
+}
+
+pub fn solve(input: String) -> anyhow::Result<()> {
+    let choices = input
+        .lines()
+        .map(|l| read_round(l.trim()))
+        .collect::<Vec<_>>();
+
+    // Part 1
+    let score = choices
+        .iter()
+        .map(|(l, r)| r.score_against(*l))
+        .sum::<u32>();
+    println!("Part 1: {score}");
+
+    Ok(())
+}