day(03): refactor parsing

Signed-off-by: Matej Focko <mfocko@redhat.com>

src/bin/day03.rs

@@ -1,25 +1,53 @@
 use std::collections::HashSet;
+use std::str::FromStr;
 
 use aoc_2022::*;
 
-use color_eyre::eyre::Result;
+use color_eyre::eyre::{Report, Result};
 use tracing::*;
 use tracing_subscriber::EnvFilter;
 
-type Input = Vec<(HashSet<i32>, HashSet<i32>)>;
+struct Backpack(HashSet<i32>, HashSet<i32>);
+
+type Input = Vec<Backpack>;
 type Output = i32;
 
+impl FromStr for Backpack {
+    type Err = Report;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let mut left: HashSet<i32> = HashSet::new();
+        let mut right: HashSet<i32> = HashSet::new();
+
+        let mid = s.len() / 2;
+        for (i, c) in s.chars().enumerate() {
+            let s = if i < mid { &mut left } else { &mut right };
+
+            s.insert(
+                c as i32
+                    + if c.is_ascii_lowercase() {
+                        1 - 'a' as i32
+                    } else {
+                        27 - 'A' as i32
+                    },
+            );
+        }
+
+        Ok(Backpack(left, right))
+    }
+}
+
 fn part_1(input: &Input) -> Output {
     input
         .iter()
-        .map(|(left, right)| left.intersection(right).sum::<i32>())
+        .map(|Backpack(left, right)| left.intersection(right).sum::<i32>())
         .sum()
 }
 
 fn part_2(input: &Input) -> Output {
     input
         .iter()
-        .map(|(left, right)| left.union(right).cloned().collect())
+        .map(|Backpack(left, right)| left.union(right).cloned().collect())
         .collect::<Vec<HashSet<i32>>>()
         .chunks(3)
         .map(|sets| {
@@ -36,26 +64,7 @@ fn part_2(input: &Input) -> Output {
 }
 
 fn parse_input(pathname: &str) -> Input {
-    file_to_lines(pathname)
-        .iter()
-        .map(|line| {
-            let mut left: HashSet<i32> = HashSet::new();
-            let mut right: HashSet<i32> = HashSet::new();
-
-            let mid = line.len() / 2;
-            for (i, c) in line.chars().enumerate() {
-                let s = if i < mid { &mut left } else { &mut right };
-
-                s.insert(if c < 'a' {
-                    c as i32 - 'A' as i32 + 27
-                } else {
-                    c as i32 - 'a' as i32 + 1
-                });
-            }
-
-            (left, right)
-        })
-        .collect()
+    file_to_structs(pathname)
 }
 
 fn main() -> Result<()> {