day(25): sprinkle in some traits

Signed-off-by: Matej Focko <me@mfocko.xyz>

src/bin/day25.rs

@@ -1,56 +1,76 @@
-use std::{char::from_digit, collections::HashMap};
+use std::{char::from_digit, collections::HashMap, fmt::Display, str::FromStr};
 
 use aoc_2022::*;
 
-type Input = Vec<String>;
+type Input = Vec<SpecialFuelUnits>;
 type Output = String;
 
-fn from_snafu(s: &str) -> isize {
-    (0..)
-        .zip(s.chars().rev())
-        .map(|(e, d)| {
-            5_isize.pow(e)
-                * match d {
-                    '-' => -1,
-                    '=' => -2,
-                    _ => d.to_digit(10).unwrap().try_into().unwrap(),
-                }
-        })
-        .sum()
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
+struct SpecialFuelUnits {
+    value: i64,
 }
 
-fn to_snafu(mut n: isize) -> String {
-    let mut digits: Vec<char> = Vec::new();
+impl FromStr for SpecialFuelUnits {
+    type Err = Report;
 
-    while n > 0 {
-        let mut d = n % 5;
-        if d > 2 {
-            n += 5 - d;
-            d -= 5;
+    fn from_str(s: &str) -> std::result::Result<Self, Self::Err> {
+        let value = (0..)
+            .zip(s.chars().rev())
+            .map(|(e, d)| {
+                5_i64.pow(e)
+                    * match d {
+                        '-' => -1,
+                        '=' => -2,
+                        _ => d.to_digit(10).unwrap().try_into().unwrap(),
+                    }
+            })
+            .sum();
+
+        Ok(Self { value })
+    }
+}
+
+impl Display for SpecialFuelUnits {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let mut n = self.value;
+        let mut digits: Vec<char> = Vec::new();
+
+        while n > 0 {
+            let mut d = n % 5;
+            if d > 2 {
+                n += 5 - d;
+                d -= 5;
+            }
+
+            digits.push(match d {
+                -1 => '-',
+                -2 => '=',
+                _ => from_digit(d as u32, 10).unwrap(),
+            });
+
+            n /= 5;
         }
 
-        digits.push(match d {
-            -1 => '-',
-            -2 => '=',
-            _ => from_digit(d as u32, 10).unwrap(),
-        });
+        digits.reverse();
 
-        n /= 5;
+        write!(f, "{}", digits.iter().join(""))
     }
+}
 
-    digits.reverse();
-
-    digits.iter().join("")
+impl From<i64> for SpecialFuelUnits {
+    fn from(value: i64) -> Self {
+        Self { value }
+    }
 }
 
 struct Day25;
 impl Solution<Input, Output> for Day25 {
     fn parse_input<P: AsRef<Path>>(pathname: P) -> Input {
-        file_to_lines(pathname)
+        file_to_structs(pathname)
     }
 
     fn part_1(input: &Input) -> Output {
-        to_snafu(input.iter().map(|s| from_snafu(s)).sum())
+        SpecialFuelUnits::from(input.iter().map(|s| s.value).sum::<i64>()).to_string()
     }
 
     fn part_2(_input: &Input) -> Output {
@@ -71,7 +91,7 @@ test_sample!(
 );
 
 lazy_static! {
-    static ref EXAMPLES: HashMap<isize, &'static str> = HashMap::from([
+    static ref EXAMPLES: HashMap<i64, &'static str> = HashMap::from([
         (1, "1"),
         (2, "2"),
         (3, "1="),
@@ -108,15 +128,15 @@ mod day_25_snafu {
 
     #[test]
     fn test_from() {
-        for (n, s) in EXAMPLES.iter() {
-            assert_eq!(from_snafu(s), *n);
+        for (&n, s) in EXAMPLES.iter() {
+            assert_eq!(s.parse::<SpecialFuelUnits>().unwrap().value, n);
         }
     }
 
     #[test]
     fn test_to() {
-        for (n, s) in EXAMPLES.iter() {
-            assert_eq!(to_snafu(*n), s.to_string());
+        for (&n, s) in EXAMPLES.iter() {
+            assert_eq!(SpecialFuelUnits::from(n).to_string(), s.to_string());
         }
     }
 }