Complete part 2 of day 2

day2/src/main.rs

@@ -1,6 +1,46 @@
 use std::error::Error;
 use std::fs;
 
+#[derive(Debug, Copy, Clone)]
+enum Calculation {
+    ByMove,
+    ByOutcome,
+}
+use Calculation::*;
+
+// ----------------------------------------------------------------------------
+
+#[derive(Debug, Copy, Clone)]
+enum Outcome {
+    Win,
+    Draw,
+    Lose,
+}
+use Outcome::*;
+
+impl From<char> for Outcome {
+    fn from(c: char) -> Self {
+        match c {
+            'X' => Lose,
+            'Y' => Draw,
+            'Z' => Win,
+            _ => panic!("Invalid char: {}", c),
+        }
+    }
+}
+
+impl Outcome {
+    fn get_score(self) -> u32 {
+        match self {
+            Lose => 0,
+            Draw => 3,
+            Win => 6,
+        }
+    }
+}
+
+// ----------------------------------------------------------------------------
+
 #[derive(Debug, Copy, Clone)]
 enum Shape {
     Rock,
@@ -21,31 +61,56 @@ impl From<char> for Shape {
 }
 
 impl Shape {
-    fn get_score(&self) -> u32 {
+    fn get_score(self) -> u32 {
         match self {
             Rock => 1,
             Paper => 2,
             Scissors => 3,
         }
     }
-}
 
-fn get_outcome_score(them: Shape, you: Shape) -> u32 {
-    match (them, you) {
-        // Loss
-        (Rock, Scissors) | (Paper, Rock) | (Scissors, Paper) => 0,
+    fn get_outcome(self, outcome: char) -> Shape {
+        let outcome = Outcome::from(outcome);
 
-        // Tie
-        (Rock, Rock) | (Paper, Paper) | (Scissors, Scissors) => 3,
-
-        // Win
-        (Rock, Paper) | (Paper, Scissors) | (Scissors, Rock) => 6,
+        match self {
+            Rock => match outcome {
+                Win => Paper,
+                Draw => Rock,
+                Lose => Scissors,
+            },
+            Paper => match outcome {
+                Win => Scissors,
+                Draw => Paper,
+                Lose => Rock,
+            },
+            Scissors => match outcome {
+                Win => Rock,
+                Draw => Scissors,
+                Lose => Paper,
+            },
+        }
     }
 }
 
-fn get_round_score(them: char, you: char) -> u32 {
+// ----------------------------------------------------------------------------
+
+fn get_outcome_score(them: Shape, you: Shape) -> u32 {
+    match (them, you) {
+        (Rock, Scissors) | (Paper, Rock) | (Scissors, Paper) => Lose,
+
+        (Rock, Rock) | (Paper, Paper) | (Scissors, Scissors) => Draw,
+
+        (Rock, Paper) | (Paper, Scissors) | (Scissors, Rock) => Win,
+    }
+    .get_score()
+}
+
+fn get_round_score(them: char, you: char, score_type: Calculation) -> u32 {
     let them = Shape::from(them);
-    let you = Shape::from(you);
+    let you = match score_type {
+        ByMove => Shape::from(you),
+        ByOutcome => them.get_outcome(you),
+    };
 
     let shape_score = you.get_score();
     let outcome_score = get_outcome_score(them, you);
@@ -53,28 +118,34 @@ fn get_round_score(them: char, you: char) -> u32 {
     shape_score + outcome_score
 }
 
-fn get_scores(lines: Vec<&str>) -> Vec<u32> {
+fn get_scores(lines: Vec<&str>, score_type: Calculation) -> Vec<u32> {
     lines
         .into_iter()
         .map(|line| {
             // This is trying to be too clever
             let [them, _, you]: [char; 3] = line.chars().collect::<Vec<char>>().try_into().unwrap();
 
-            get_round_score(them, you)
+            get_round_score(them, you, score_type)
         })
         .collect()
 }
 
+fn get_total(lines: &Vec<&str>, score_type: Calculation) -> u32 {
+    get_scores(lines.clone(), score_type)
+        .into_iter()
+        .reduce(|accum, item| accum + item)
+        .unwrap()
+}
+
 fn main() -> Result<(), Box<dyn Error>> {
     let file_str = fs::read_to_string("input.txt")?;
     let lines: Vec<&str> = file_str.lines().collect();
-    let scores = get_scores(lines);
-    let total = scores
-        .into_iter()
-        .reduce(|accum, item| accum + item)
-        .unwrap();
 
-    println!("Part 1: Final score: {}", total);
+    let part1_total = get_total(&lines, ByMove);
+    let part2_total = get_total(&lines, ByOutcome);
+
+    println!("Part 1: Final score: {}", part1_total);
+    println!("Part 2: Final score: {}", part2_total);
 
     Ok(())
 }