2022 day3/rust: cleanup

2022/day3/rust/src/main.rs

@@ -7,38 +7,52 @@ fn item_priority(item: char) -> u32 {
     match item {
         'a'..='z' => item as u32 - 'a' as u32 + 1,
         'A'..='Z' => item as u32 - 'A' as u32 + 27,
-        _ => unreachable!(),
+        _ => panic!("invalid item {item}"),
     }
 }
 
+struct Rucksack {
+    left: HashSet<char>,
+    right: HashSet<char>,
+}
+
 fn main() {
     let mut data = String::new();
     stdin().read_to_string(&mut data).unwrap();
 
-    let mut sum = 0;
-    for line in data.lines() {
+    let sacks: Vec<_> = data
+        .lines()
+        .map(|line| {
             let (left, right) = line.split_at(line.len() / 2);
             assert_eq!(left.len(), right.len());
 
             let left: HashSet<_> = left.chars().collect();
             let right: HashSet<_> = right.chars().collect();
 
-        let common = *left.intersection(&right).next().unwrap();
-        sum += item_priority(common);
-    }
+            Rucksack { left, right }
+        })
+        .collect();
 
-    println!("{}", sum);
-
-    let mut sum = 0;
-    for lines in data.lines().collect::<Vec<_>>().chunks(3) {
-        let common = lines
+    let sum1: u32 = sacks
         .iter()
-            .map(|line| line.chars().collect::<HashSet<_>>())
-            .reduce(|l, r| &l & &r)
+        .map(|sack| item_priority(*sack.left.intersection(&sack.right).next().unwrap()))
+        .sum();
+
+    let sum2: u32 = sacks
+        .chunks(3)
+        .into_iter()
+        .map(|sacks| {
+            let common = sacks
+                .iter()
+                .map(|sack| &sack.left | &sack.right)
+                .reduce(|a, b| &a & &b)
                 .unwrap();
             assert_eq!(common.len(), 1);
 
-        sum += item_priority(common.into_iter().next().unwrap());
-    }
-    println!("{}", sum);
+            item_priority(common.into_iter().next().unwrap())
+        })
+        .sum();
+
+    println!("{}", sum1);
+    println!("{}", sum2);
 }