Quest 1 / Part 3

src/bin/quest-1-part-3.rs

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+use std::{collections::HashMap, path::PathBuf};
+
+type Result<T> = std::result::Result<T, Box<dyn std::error::Error>>;
+
+fn main() -> Result<()> {
+    let file_path = PathBuf::from("./data/quest-1-part-3.txt");
+    let data = std::fs::read_to_string(file_path)?;
+    let counter = quest_part_3(&data);
+    println!("Quest 1 / Part 3: {counter}");
+    Ok(())
+}
+
+#[derive(PartialEq, Eq)]
+enum Position {
+    Left,
+    Middle,
+    Right,
+}
+#[derive(Debug, Default)]
+struct Fight {
+    left: i32,
+    middle: i32,
+    right: i32,
+    combatants: i32,
+}
+
+fn quest_part_3(data: &str) -> i32 {
+    let table = HashMap::from([('A', 0), ('B', 1), ('C', 3), ('D', 5)]);
+    let mut counter = 0;
+
+    let mut position = Position::Left;
+    let mut fight = Fight::default();
+    for beast in data.chars() {
+        match (&position, table.get(&beast)) {
+            (Position::Left, None) => {
+                fight.left = 0;
+                fight.combatants = 0;
+            }
+            (Position::Left, Some(score)) => {
+                fight.left = *score;
+                fight.combatants = 1;
+            }
+            (Position::Middle, None) => {
+                fight.middle = 0;
+            }
+            (Position::Middle, Some(score)) => {
+                fight.middle = *score;
+                fight.combatants += 1;
+            }
+            (Position::Right, None) => {
+                fight.right = 0;
+            }
+            (Position::Right, Some(score)) => {
+                fight.right = *score;
+                fight.combatants += 1;
+            }
+        }
+        if position == Position::Right {
+            let score = fight.left + fight.middle + fight.right;
+            let bonus = match fight.combatants {
+                3 => 6, // two per combatant
+                2 => 2, // one per combatant
+                1 => 0, // no bonus
+                _ => 0, // fail-safe
+            };
+            counter += score + bonus;
+            println!("{fight:?} - {score} - {bonus} -> {} --> {counter}", score + bonus);
+        }
+        position = match &position {
+            Position::Left => Position::Middle,
+            Position::Middle => Position::Right,
+            Position::Right => Position::Left,
+        }
+    }
+    counter
+}
+
+#[cfg(test)]
+mod tests {
+    use super::quest_part_3;
+
+    #[test]
+    fn sample() {
+        let data = "xBxAAABCDxCC";
+        let result = quest_part_3(data);
+        assert_eq!(result, 30);
+    }
+}