Add day2

src/bin/day2.rs

@@ -0,0 +1,105 @@
+use aoc2022::StdError;
+use std::fs::File;
+use std::io::{BufRead, BufReader};
+
+#[derive(PartialEq, Clone, Copy)]
+enum Move {
+    Rock,
+    Paper,
+    Scissors,
+}
+
+enum Outcome {
+    Win,
+    Loss,
+    Draw,
+}
+
+impl Outcome {
+    fn from_char(c: char) -> Option<Self> {
+        match c {
+            'X' => Some(Self::Loss),
+            'Y' => Some(Self::Draw),
+            'Z' => Some(Self::Win),
+            _ => None,
+        }
+    }
+
+    fn score(&self) -> u8 {
+        match self {
+            Self::Win => 6,
+            Self::Draw => 3,
+            Self::Loss => 0,
+        }
+    }
+}
+
+impl Move {
+    fn from_char(c: char) -> Option<Self> {
+        match c {
+            'A' | 'X' => Some(Self::Rock),
+            'B' | 'Y' => Some(Self::Paper),
+            'C' | 'Z' => Some(Self::Scissors),
+            _ => None,
+        }
+    }
+
+    fn outcome_for_move(&self, other: &Self) -> Outcome {
+        match (self, other) {
+            (Self::Rock, Self::Rock)
+            | (Self::Paper, Self::Paper)
+            | (Self::Scissors, Self::Scissors) => Outcome::Draw,
+            (Self::Rock, Self::Scissors) => Outcome::Win,
+            (Self::Rock, Self::Paper) => Outcome::Loss,
+            (Self::Paper, Self::Rock) => Outcome::Win,
+            (Self::Paper, Self::Scissors) => Outcome::Loss,
+            (Self::Scissors, Self::Paper) => Outcome::Win,
+            (Self::Scissors, Self::Rock) => Outcome::Loss,
+        }
+    }
+
+    fn move_for_outcome(&self, outcome: Outcome) -> Move {
+        match (self, outcome) {
+            (Self::Rock, Outcome::Win) => Move::Paper,
+            (Self::Rock, Outcome::Loss) => Move::Scissors,
+            (Self::Paper, Outcome::Win) => Move::Scissors,
+            (Self::Paper, Outcome::Loss) => Move::Rock,
+            (Self::Scissors, Outcome::Win) => Move::Rock,
+            (Self::Scissors, Outcome::Loss) => Move::Paper,
+            (_, Outcome::Draw) => *self,
+        }
+    }
+
+    fn score(&self) -> u8 {
+        match self {
+            Self::Rock => 1,
+            Self::Paper => 2,
+            Self::Scissors => 3,
+        }
+    }
+}
+
+fn main() -> StdError<()> {
+    let lines: Vec<_> = BufReader::new(File::open("input/day2.txt")?)
+        .lines()
+        .filter_map(Result::ok)
+        .map(|l| {
+            let spl: Vec<_> = l.chars().collect();
+            assert!(spl.len() == 3);
+            (spl[0], spl[2])
+        })
+        .collect();
+    let part1: u32 = lines
+        .iter()
+        .map(|(a, b)| (Move::from_char(*a).unwrap(), Move::from_char(*b).unwrap()))
+        .map(|(opponent, you)| (you.score() + you.outcome_for_move(&opponent).score()) as u32)
+        .sum();
+    println!("Part 1: {}", part1);
+    let part2: u32 = lines
+        .iter()
+        .map(|(a, b)| (Move::from_char(*a).unwrap(), Outcome::from_char(*b).unwrap()))
+        .map(|(opp, out)| (out.score() + opp.move_for_outcome(out).score()) as u32)
+        .sum();
+    println!("Part 2: {}", part2);
+    Ok(())
+}