Day 1, 2 and 3

day2/.gitignore

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+/target

day2/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day2"
+version = "0.1.0"

day2/Cargo.toml

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+[package]
+name = "day2"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day2/src/main.rs

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+use std::fs::read_to_string;
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+enum Symbol {
+    Rock,
+    Paper,
+    Scissors,
+}
+
+impl From<char> for Symbol {
+    fn from(value: char) -> Self {
+        match value {
+            'A' => Self::Rock,
+            'B' => Self::Paper,
+            'C' => Self::Scissors,
+            'X' => Self::Rock,
+            'Y' => Self::Paper,
+            'Z' => Self::Scissors,
+            _ => panic!("invalid input"),
+        }
+    }
+}
+
+#[derive(Debug, PartialEq, Eq, Clone, Copy)]
+enum Outcome {
+    Win,
+    Draw,
+    Lose,
+}
+
+impl From<char> for Outcome {
+    fn from(value: char) -> Self {
+        match value {
+            'X' => Self::Lose,
+            'Y' => Self::Draw,
+            'Z' => Self::Win,
+            _ => panic!("invalid input"),
+        }
+    }
+}
+
+impl Symbol {
+    fn play(self, opponent: Self) -> Outcome {
+        if self == opponent {
+            Outcome::Draw
+        } else if (self == Self::Rock && opponent == Self::Scissors)
+            || (self == Self::Paper && opponent == Self::Rock)
+            || (self == Self::Scissors && opponent == Self::Paper)
+        {
+            Outcome::Win
+        } else {
+            Outcome::Lose
+        }
+    }
+}
+
+fn score(play: Symbol, result: Outcome) -> u32 {
+    let score = match play {
+        Symbol::Rock => 1,
+        Symbol::Paper => 2,
+        Symbol::Scissors => 3,
+    };
+    let score2 = match result {
+        Outcome::Lose => 0,
+        Outcome::Draw => 3,
+        Outcome::Win => 6,
+    };
+    score + score2
+}
+
+fn get_play(opponent: Symbol, outcome: Outcome) -> Symbol {
+    match outcome {
+        Outcome::Win => match opponent {
+            Symbol::Rock => Symbol::Paper,
+            Symbol::Paper => Symbol::Scissors,
+            Symbol::Scissors => Symbol::Rock,
+        },
+        Outcome::Draw => opponent,
+        Outcome::Lose => match opponent {
+            Symbol::Rock => Symbol::Scissors,
+            Symbol::Paper => Symbol::Rock,
+            Symbol::Scissors => Symbol::Paper,
+        },
+    }
+}
+
+fn initial(input: &str) -> (u32, u32) {
+    let first = input
+        .split_terminator('\n')
+        .map(|line| {
+            line.split_whitespace()
+                .map(|s| Symbol::from(s.chars().next().unwrap()))
+                .collect::<Vec<_>>()
+        })
+        .map(|p| score(p[1], p[1].play(p[0])))
+        .sum();
+    let second = input
+        .split_terminator('\n')
+        .map(|line| {
+            let chars: Vec<_> = line
+                .split_whitespace()
+                .map(|s| s.chars().next().unwrap())
+                .collect();
+            let opponent = Symbol::from(chars[0]);
+            let outcome = Outcome::from(chars[1]);
+            let play = get_play(opponent, outcome);
+            score(play, outcome)
+        })
+        .sum();
+    (first, second)
+}
+
+fn main() {
+    let input = read_to_string("input.txt").expect("input needed");
+    let score = initial(&input);
+    println!("score: {score:?}");
+}