Day 02

src/day02/mod.rs

@@ -1,17 +1,78 @@
 use crate::read;
 
 struct Hand {
-    pub letter: char,
+    pub letter: char
+}
+
+impl Hand {
+    pub fn score(&self) -> i32 {
+        match self.letter {
+            'A' => 1,
+            'B' => 2,
+            'C' => 3,
+            'X' => 1,
+            'Y' => 2,
+            'Z' => 3,
+            _ => panic!("Unknown hand {}", self.letter)
+        }
+    }
+
+    pub fn outcome(&self, other: &Hand) -> i32 {
+        match self.score() - other.score() {
+            -1 => 0,
+            -2 => 6,
+            0 => 3,
+            1 => 6,
+            2 => 0,
+            _ => panic!("Unknown match {} vs {}", self.letter, other.letter)
+        }
+    }
+
+    pub fn outcome_b(&self) -> i32 {
+        match self.letter {
+            'X' => 0,
+            'Y' => 3,
+            'Z' => 6,
+            _ => panic!("Unknown outcome {}", self.letter)
+        }
+    }
+
+    pub fn for_outcome(&self, enemy: &Hand) -> Self {
+        let letter = match (self.outcome_b(), enemy.letter) {
+            (o, l) if o == 3 => l,
+            (o, l) if o == 0 && l == 'A' => 'C',
+            (o, l) if o == 0 && l == 'B' => 'A',
+            (o, l) if o == 0 && l == 'C' => 'B',
+            (o, l) if o == 6 && l == 'A' => 'B',
+            (o, l) if o == 6 && l == 'B' => 'C',
+            (o, l) if o == 6 && l == 'C' => 'A',
+            (o, l)=> panic!("Unknown pairing {}/{}", o, l)
+        };
+       Self {
+           letter
+       }
+    }
 }
 
 struct Round {
-    enemy: Hand,
+    pub enemy: Hand,
-    me: Hand,
+    pub me: Hand,
+}
+
+impl Round {
+    pub fn score(&self) -> i32 {
+        self.me.score() + self.me.outcome(&self.enemy)
+    }
+
+    pub fn score_b(&self) -> i32 {
+        let me = self.me.for_outcome(&self.enemy);
+        me.score() + self.me.outcome_b()
+    }
 }
 
 pub fn run() {
     let input = read("02");
-    let lines = input.lines().map(|l| {
+    let rounds = input.lines().map(|l| {
         let hands = l.split(' ').collect::<Vec<_>>();
         Round {
             enemy: Hand {
@@ -21,17 +82,24 @@ pub fn run() {
                 letter: hands[1].chars().next().unwrap(),
             },
         }
-    });
+    }
+    ).collect::<Vec<_>>();
 
     #[cfg(feature = "part1")]
     {
-        let a = "TODO";
+        let a: i32 = rounds
+            .iter()
+            .map(|r|r.score())
+            .sum();
         eprintln!("Day 2, Part 01: {}", a);
     }
 
     #[cfg(feature = "part2")]
     {
-        let b = "TODO";
+        let b: i32 = rounds
+            .iter()
+            .map(|r|r.score_b())
+            .sum();
         eprintln!("Day 2, Part 02: {}", b);
     }
 }