day 2

src/days/day2.rs

@@ -0,0 +1,98 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+
+#[derive(Clone, Copy)]
+enum Rps {
+    Rock,
+    Paper,
+    Scissors,
+}
+
+#[derive(Clone, Copy)]
+enum Xyz {
+    X,
+    Y,
+    Z,
+}
+
+impl Xyz {
+    fn to_rps(self) -> Rps {
+        match self {
+            Xyz::X => Rps::Rock,
+            Xyz::Y => Rps::Paper,
+            Xyz::Z => Rps::Scissors,
+        }
+    }
+
+    fn part_two_stuff(self, opp: Rps) -> u32 {
+        match (self, opp) {
+            // need to lose
+            (Xyz::X, Rps::Rock) => Rps::Scissors,
+            (Xyz::X, Rps::Paper) => Rps::Rock,
+            (Xyz::X, Rps::Scissors) => Rps::Paper,
+            // need to draw
+            (Xyz::Y, _) => opp,
+            // need to win
+            (Xyz::Z, Rps::Rock) => Rps::Paper,
+            (Xyz::Z, Rps::Paper) => Rps::Scissors,
+            (Xyz::Z, Rps::Scissors) => Rps::Rock,
+        }
+        .score_against(opp)
+    }
+}
+
+impl Rps {
+    fn score_against(self, opp: Rps) -> u32 {
+        // 1 for Rock, 2 for Paper, 3 for Scissors
+        // 0 for loss, 3 for tie, 6 for win
+        #[allow(clippy::identity_op)]
+        match (self, opp) {
+            (Rps::Rock, Rps::Rock) => 1 + 3,
+            (Rps::Rock, Rps::Paper) => 1 + 0,
+            (Rps::Rock, Rps::Scissors) => 1 + 6,
+            (Rps::Paper, Rps::Rock) => 2 + 6,
+            (Rps::Paper, Rps::Paper) => 2 + 3,
+            (Rps::Paper, Rps::Scissors) => 2 + 0,
+            (Rps::Scissors, Rps::Rock) => 3 + 0,
+            (Rps::Scissors, Rps::Paper) => 3 + 6,
+            (Rps::Scissors, Rps::Scissors) => 3 + 3,
+        }
+    }
+}
+
+#[aoc_generator(day2)]
+fn day1_generator(s: &str) -> Vec<(Rps, Xyz)> {
+    s.lines()
+        .map(|l| {
+            (
+                match l.chars().next().unwrap() {
+                    'A' => Rps::Rock,
+                    'B' => Rps::Paper,
+                    'C' => Rps::Scissors,
+                    _ => panic!(),
+                },
+                match l.chars().nth(2).unwrap() {
+                    'X' => Xyz::X,
+                    'Y' => Xyz::Y,
+                    'Z' => Xyz::Z,
+                    _ => panic!(),
+                },
+            )
+        })
+        .collect()
+}
+
+#[aoc(day2, part1)]
+fn day1_part1(input: &[(Rps, Xyz)]) -> u32 {
+    input
+        .iter()
+        .map(|&(opp, me)| me.to_rps().score_against(opp))
+        .sum()
+}
+
+#[aoc(day2, part2)]
+fn day1_part2(input: &[(Rps, Xyz)]) -> u32 {
+    input
+        .iter()
+        .map(|&(opp, target_xyz)| target_xyz.part_two_stuff(opp))
+        .sum()
+}

src/lib.rs

@@ -2,6 +2,7 @@ use aoc_runner_derive::aoc_lib;
 
 mod days {
     mod day1;
+    mod day2;
 }
 
 aoc_lib! { year = 2022 }