Rust Day 2

rust/Cargo.lock

@@ -4,4 +4,4 @@ version = 3
 
 [[package]]
 name = "advent-of-code"
-version = "22.1.2"
+version = "22.2.2"

rust/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "advent-of-code"
-version = "22.1.2"
+version = "22.2.2"
 edition = "2021"
 resolver = "2"
 
@@ -30,3 +30,7 @@ path = "src/day00/main.rs"
 [[bin]]
 name = "day01"
 path = "src/day01/main.rs"
+
+[[bin]]
+name = "day02"
+path = "src/day02/main.rs"

rust/src/day02/main.rs

@@ -0,0 +1,161 @@
+const INPUT: &str = include_str!("input.txt");
+
+mod part_1;
+use std::str::FromStr;
+
+use part_1::part_1;
+mod part_2;
+use part_2::part_2;
+
+#[derive(Clone, Copy)]
+pub(crate) enum Shape {
+    Rock,
+    Paper,
+    Scissors,
+}
+
+#[derive(Clone, Copy)]
+pub(crate) enum GameResult {
+    Win,
+    Tie,
+    Loss,
+}
+
+impl Shape {
+    fn play_against(&self, other: &Shape) -> GameResult {
+        match self {
+            Shape::Rock => match other {
+                Shape::Rock => GameResult::Tie,
+                Shape::Paper => GameResult::Loss,
+                Shape::Scissors => GameResult::Win,
+            },
+            Shape::Paper => match other {
+                Shape::Rock => GameResult::Win,
+                Shape::Paper => GameResult::Tie,
+                Shape::Scissors => GameResult::Loss,
+            },
+            Shape::Scissors => match other {
+                Shape::Rock => GameResult::Loss,
+                Shape::Paper => GameResult::Win,
+                Shape::Scissors => GameResult::Tie,
+            },
+        }
+    }
+
+    fn get_response_for_result(&self, result: &GameResult) -> Self {
+        match self {
+            Shape::Rock => match result {
+                GameResult::Tie => Shape::Rock,
+                GameResult::Loss => Shape::Scissors,
+                GameResult::Win => Shape::Paper,
+            },
+            Shape::Paper => match result {
+                GameResult::Win => Shape::Scissors,
+                GameResult::Tie => Shape::Paper,
+                GameResult::Loss => Shape::Rock,
+            },
+            Shape::Scissors => match result {
+                GameResult::Loss => Shape::Paper,
+                GameResult::Win => Shape::Rock,
+                GameResult::Tie => Shape::Scissors,
+            },
+        }
+    }
+}
+
+impl From<&Shape> for u64 {
+    fn from(shape: &Shape) -> Self {
+        match shape {
+            Shape::Rock => 1,
+            Shape::Paper => 2,
+            Shape::Scissors => 3,
+        }
+    }
+}
+
+impl From<&GameResult> for u64 {
+    fn from(game_result: &GameResult) -> Self {
+        match game_result {
+            GameResult::Win => 6,
+            GameResult::Tie => 3,
+            GameResult::Loss => 0,
+        }
+    }
+}
+
+#[derive(Debug)]
+pub(crate) struct ParseShapeError;
+
+impl FromStr for Shape {
+    type Err = ParseShapeError;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        assert_eq!(s.len(), 1);
+        let Some(character) = s.bytes().next() else {
+            return Err(ParseShapeError);
+        };
+
+        match character {
+            b'A' | b'X' => Ok(Shape::Rock),
+            b'B' | b'Y' => Ok(Shape::Paper),
+            b'C' | b'Z' => Ok(Shape::Scissors),
+            _ => Err(ParseShapeError),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub(crate) struct ParseGameResultError;
+
+impl FromStr for GameResult {
+    type Err = ParseGameResultError;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        assert_eq!(s.len(), 1);
+        let Some(character) = s.bytes().next() else {
+            return Err(ParseGameResultError);
+        };
+
+        match character {
+            b'X' => Ok(GameResult::Loss),
+            b'Y' => Ok(GameResult::Tie),
+            b'Z' => Ok(GameResult::Win),
+            _ => Err(ParseGameResultError),
+        }
+    }
+}
+
+fn parse_input_part_1() -> Vec<[Shape; 2]> {
+    INPUT
+        .split('\n')
+        .map(|round_string| {
+            let round = round_string
+                .split(' ')
+                .map(|play| {
+                    Shape::from_str(play).unwrap_or_else(|_| panic!("Found invalid play {play}"))
+                })
+                .take(2)
+                .collect::<Vec<_>>();
+            [round[0], round[1]]
+        })
+        .collect::<Vec<_>>()
+}
+
+fn parse_input_part_2() -> Vec<(Shape, GameResult)> {
+    INPUT
+        .split('\n')
+        .map(|round_string| {
+            let round = round_string.split(' ').take(2).collect::<Vec<_>>();
+            assert_eq!(round.len(), 2);
+            let enemy_shape = Shape::from_str(round[0])
+                .unwrap_or_else(|_| panic!("Found invalid play {}", round[0]));
+            let desired_result = GameResult::from_str(round[1])
+                .unwrap_or_else(|_| panic!("Found invalid desired result {}", round[1]));
+
+            (enemy_shape, desired_result)
+        })
+        .collect::<Vec<_>>()
+}
+
+pub fn main() {
+    part_1(parse_input_part_1().as_slice());
+    part_2(parse_input_part_2().as_slice());
+}

rust/src/day02/part_1.rs

@@ -0,0 +1,8 @@
+use crate::Shape;
+
+pub(crate) fn part_1(input: &[[Shape; 2]]) {
+    let final_score = input.iter().fold(0u64, |acc, [enemy, mine]| {
+        acc + u64::from(&mine.play_against(enemy)) + u64::from(mine)
+    });
+    println!("Part 1: {final_score}");
+}

rust/src/day02/part_2.rs

@@ -0,0 +1,11 @@
+use crate::{GameResult, Shape};
+
+pub(crate) fn part_2(input: &[(Shape, GameResult)]) {
+    let final_score = input
+        .iter()
+        .fold(0u64, |acc, (enemy_play, desired_result)| {
+            acc + u64::from(&enemy_play.get_response_for_result(desired_result))
+                + u64::from(desired_result)
+        });
+    println!("Part 2: {final_score}");
+}