Day 2

src/day02.rs

@@ -0,0 +1,132 @@
+use std::str::FromStr;
+
+use aoc_runner_derive::{aoc, aoc_generator};
+
+#[derive(Copy, Clone, Debug)]
+pub struct InvalidMove;
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum Move {
+    Rock,
+    Paper,
+    Scissors,
+}
+
+impl Move {
+    fn shape_score(self) -> u64 {
+        match self {
+            Self::Rock => 1,
+            Self::Paper => 2,
+            Self::Scissors => 3,
+        }
+    }
+
+    fn round_score(self, opp: Self) -> u64 {
+        if self == opp {
+            return 3;
+        }
+        match (self, opp) {
+            (Self::Rock, Self::Scissors) => 6,
+            (Self::Scissors, Self::Paper) => 6,
+            (Self::Paper, Self::Rock) => 6,
+            _ => 0,
+        }
+    }
+}
+
+impl FromStr for Move {
+    type Err = InvalidMove;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        // X Y and Z are treated as moves because part 1 uses them as moves even though they are
+        // not.
+        match s {
+            "A" | "X" => Ok(Self::Rock),
+            "B" | "Y" => Ok(Self::Paper),
+            "C" | "Z" => Ok(Self::Scissors),
+            _ => Err(InvalidMove),
+        }
+    }
+}
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum Outcome {
+    Lose,
+    Draw,
+    Win,
+}
+
+impl Outcome {
+    fn compute_move(&self, opp: Move) -> Move {
+        match self {
+            Outcome::Lose => match opp {
+                Move::Rock => Move::Scissors,
+                Move::Paper => Move::Rock,
+                Move::Scissors => Move::Paper,
+            },
+            Outcome::Draw => opp,
+            Outcome::Win => match opp {
+                Move::Rock => Move::Paper,
+                Move::Paper => Move::Scissors,
+                Move::Scissors => Move::Rock,
+            },
+        }
+    }
+}
+
+#[derive(Copy, Clone, Debug)]
+pub struct InvalidOutcome;
+
+impl FromStr for Outcome {
+    type Err = InvalidOutcome;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s {
+            "X" => Ok(Self::Lose),
+            "Y" => Ok(Self::Draw),
+            "Z" => Ok(Self::Win),
+            _ => Err(InvalidOutcome),
+        }
+    }
+}
+
+#[aoc_generator(day2, part1)]
+pub fn input_generator_part1(input: &str) -> Vec<(Move, Move)> {
+    input
+        .lines()
+        .map(|line| {
+            let (opp, you) = line.split_once(' ').unwrap();
+            (opp.parse().unwrap(), you.parse().unwrap())
+        })
+        .collect::<Vec<_>>()
+}
+
+#[aoc(day2, part1)]
+pub fn solve_part1(input: &[(Move, Move)]) -> u64 {
+    input
+        .iter()
+        .map(|&(opp, you)| you.shape_score() + you.round_score(opp))
+        .sum()
+}
+
+#[aoc_generator(day2, part2)]
+pub fn input_generator_part2(input: &str) -> Vec<(Move, Outcome)> {
+    input
+        .lines()
+        .map(|line| {
+            let (opp, outcome) = line.split_once(' ').unwrap();
+            (opp.parse().unwrap(), outcome.parse().unwrap())
+        })
+        .collect::<Vec<_>>()
+}
+
+#[aoc(day2, part2)]
+pub fn solve_part2(input: &[(Move, Outcome)]) -> u64 {
+    input
+        .iter()
+        .map(|&(opp, outcome)| {
+            let you = outcome.compute_move(opp);
+            you.shape_score() + you.round_score(opp)
+        })
+        .sum()
+}

src/lib.rs

@@ -1,5 +1,6 @@
 use aoc_runner_derive::aoc_lib;
 
 pub mod day01;
+pub mod day02;
 
 aoc_lib! { year = 2022 }