feat: day2

Signed-off-by: Louis Vallat <louis@louis-vallat.xyz>

.gitlab-ci.yml

@@ -9,3 +9,7 @@ day-1:
   script:
     - cd day1; cargo run --release ./input
 
+day-2:
+  stage: build
+  script:
+    - cd day2; cargo run --release ./input

day2/Cargo.toml

@@ -0,0 +1,8 @@
+[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

@@ -0,0 +1,76 @@
+use std::{fs, env, char};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+enum Moves {
+    Rock = 1,
+    Paper = 2,
+    Scissors = 3
+}
+
+impl Moves {
+    fn get_move_from_letter(c: char) -> Moves {
+        match c {
+            'A' | 'X' => Self::Rock,
+            'B' | 'Y' => Self::Paper,
+            'C' | 'Z' => Self::Scissors,
+            _ => panic!("Move '{}' is not implemented!", c)
+        }
+    }
+
+    fn get_move_from_line(s: &str) -> (Moves, Moves) {
+        let c = s.chars().collect::<Vec<char>>();
+        return (Self::get_move_from_letter(c[0]), Self::get_move_from_letter(c[2]));
+    }
+
+    fn get_winning_move(&self) -> Moves {
+        match self {
+            Self::Rock => Self::Scissors,
+            Self::Paper => Self::Rock,
+            Self::Scissors => Self::Paper
+        }
+    }
+
+    fn get_losing_move(&self) -> Moves {
+        match self {
+            Self::Scissors => Self::Rock,
+            Self::Rock => Self::Paper,
+            Self::Paper => Self::Scissors
+        }
+    }
+}
+
+fn read_input(path: &str) -> String {
+    return fs::read_to_string(path).expect("Cannot read file.");
+}
+
+fn parse_input(s: &str) -> Vec<(Moves, Moves)> {
+    return s.lines().into_iter().fold(vec![], |mut acc, x| {
+        acc.push(Moves::get_move_from_line(x));
+        return acc;
+    });
+}
+
+fn get_score_for_round(round: &(Moves, Moves)) -> i32 {
+    return round.1 as i32 +
+        if round.0 == round.1 { 3 }
+        else if round.1.get_winning_move() == round.0 { 6 }
+        else { 0 };
+}
+
+fn get_expected_score_for_round(round: &(Moves, Moves)) -> i32 {
+    return get_score_for_round(&(round.0, 
+        if round.1 == Moves::Paper { round.0 }
+        else if round.1 == Moves::Rock { round.0.get_winning_move() }
+        else { round.0.get_losing_move() }
+    ));
+}
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    for arg in args.iter().skip(1) {
+        println!("[{}]", &arg);
+        let vec_in = parse_input(&read_input(&arg));
+        println!("\t[Part 1] => Answer is '{}'.", vec_in.iter().fold(0, |acc, x| acc + get_score_for_round(&x)));
+        println!("\t[Part 2] => Answer is '{}'.", vec_in.iter().fold(0, |acc, x| acc + get_expected_score_for_round(&x)));
+    }
+}