3 files changed, 136 insertions, 1 deletions
diff --git a/2022/rust/Cargo.toml b/2022/rust/Cargo.toml
index 079c5ee..0707ddf 100644
--- a/2022/rust/Cargo.toml
+++ b/2022/rust/Cargo.toml
@@ -1,7 +1,7 @@
 [workspace]
 members = [
      "day01",
-#     "day02",
+     "day02",
 #     "day03",
 #     "day04",
 #     "day05",
diff --git a/2022/rust/day02/Cargo.toml b/2022/rust/day02/Cargo.toml
new file mode 100644
index 0000000..9377f12
--- /dev/null
+++ b/2022/rust/day02/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "day02"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+aoc = { path = "../../../common/rust/aoc" }
+anyhow = "1.0"
diff --git a/2022/rust/day02/src/main.rs b/2022/rust/day02/src/main.rs
new file mode 100644
index 0000000..d98d7b1
--- /dev/null
+++ b/2022/rust/day02/src/main.rs
@@ -0,0 +1,127 @@
+use {
+    anyhow::{
+        anyhow,
+        Context,
+        Result,
+    },
+    std::{
+        env::args,
+        fs::File,
+        io::{
+            BufRead,
+            BufReader,
+        },
+        path::Path,
+    },
+};
+
+#[derive(Clone,Copy)]
+enum Play {
+    Rock = 1,
+    Paper = 2,
+    Scissors = 3,
+}
+
+impl Play {
+    fn strategy(&self, desired: Outcome) -> Play {
+        match (self, desired) {
+            (Play::Rock,     Outcome::Lose) => Play::Scissors,
+            (Play::Rock,     Outcome::Draw) => Play::Rock,
+            (Play::Rock,     Outcome::Win)  => Play::Paper,
+            (Play::Paper,    Outcome::Lose) => Play::Rock,
+            (Play::Paper,    Outcome::Draw) => Play::Paper,
+            (Play::Paper,    Outcome::Win)  => Play::Scissors,
+            (Play::Scissors, Outcome::Lose) => Play::Paper,
+            (Play::Scissors, Outcome::Draw) => Play::Scissors,
+            (Play::Scissors, Outcome::Win)  => Play::Rock,
+        }
+    }
+}
+
+#[derive(Clone,Copy)]
+enum Outcome {
+    Lose = 0,
+    Draw = 3,
+    Win = 6,
+}
+
+struct Game {
+    opponent: Play,
+    play: Play,
+    outcome: Outcome,
+}
+
+impl Game {
+    fn outcome(&self) -> Outcome {
+        match (&self.play, &self.opponent) {
+            (Play::Rock,     Play::Rock)     => Outcome::Draw,
+            (Play::Rock,     Play::Paper)    => Outcome::Lose,
+            (Play::Rock,     Play::Scissors) => Outcome::Win,
+            (Play::Paper,    Play::Rock)     => Outcome::Win,
+            (Play::Paper,    Play::Paper)    => Outcome::Draw,
+            (Play::Paper,    Play::Scissors) => Outcome::Lose,
+            (Play::Scissors, Play::Rock)     => Outcome::Lose,
+            (Play::Scissors, Play::Paper)    => Outcome::Win,
+            (Play::Scissors, Play::Scissors) => Outcome::Draw,
+        }
+    }
+
+    fn update(&mut self) {
+        self.play = self.opponent.strategy(self.outcome);
+    }
+
+    fn score(&self) -> usize {
+        self.play as usize + self.outcome() as usize
+    }
+}
+
+fn read_input<T: AsRef<Path>>(filename: T) -> Result<Vec<Game>> {
+    let reader = BufReader::new(File::open(filename)?);
+
+    reader.lines().map(
+        |v| {
+            let s = v?;
+            let fields: Vec<_> = s.split(' ').collect();
+            let opponent = match *(fields.first().ok_or_else(|| anyhow!("Parse error"))?) {
+                "A" => Ok(Play::Rock),
+                "B" => Ok(Play::Paper),
+                "C" => Ok(Play::Scissors),
+                _ => Err(anyhow!("Invalid input")),
+            }?;
+            let ( play, outcome ) = match *(fields.get(1).ok_or_else(|| anyhow!("Parse error"))?) {
+                "X" => Ok((Play::Rock,     Outcome::Lose)),
+                "Y" => Ok((Play::Paper,    Outcome::Draw)),
+                "Z" => Ok((Play::Scissors, Outcome::Win)),
+                _ => Err(anyhow!("Invalid input")),
+            }?;
+            Ok(Game { opponent, play, outcome })
+        }
+    ).collect()
+}
+
+fn part1(input: &[Game]) -> Result<usize> {
+    Ok(input.iter().map(|game| game.score()).sum())
+}
+
+fn part2(input: &mut [Game]) -> Result<usize> {
+    Ok(input.iter_mut().map(|game| {
+        game.update();
+        game.score()
+    }).sum())
+}
+
+fn main() -> Result<()> {
+    let ( do_part_1, do_part_2 ) = aoc::do_parts();
+
+    let filename = args().nth(1).ok_or_else(|| anyhow!("Missing input filename"))?;
+    let mut input = read_input(filename).context("Could not read input")?;
+    if do_part_1 {
+        let solution = part1(&input).context("No solution for part 1")?;
+        println!("Part1, solution found to be: {}", solution);
+    }
+    if do_part_2 {
+        let solution = part2(&mut input).context("No solution for part 2")?;
+        println!("Part2, solution found to be: {}", solution);
+    }
+    Ok(())
+}