[rs] Solve 2022_03 part 1

rs/src/y2022/d03.rs

@@ -0,0 +1,30 @@
+use std::collections::HashSet;
+
+fn score(c: char) -> u32 {
+    match c {
+        'a'..='z' => c as u32 - 'a' as u32 + 1,
+        'A'..='Z' => c as u32 - 'A' as u32 + 27,
+        _ => panic!(),
+    }
+}
+
+pub fn solve(input: String) -> anyhow::Result<()> {
+    let backpacks = input
+        .lines()
+        .map(|l| l.trim())
+        .map(|l| l.split_at(l.len() / 2))
+        .collect::<Vec<_>>();
+
+    // Part 1
+    let score = backpacks
+        .iter()
+        .map(|(l, r)| {
+            let l = l.chars().collect::<HashSet<_>>();
+            let r = r.chars().collect::<HashSet<_>>();
+            l.intersection(&r).map(|c| score(*c)).sum::<u32>()
+        })
+        .sum::<u32>();
+    println!("Part 1: {score}");
+
+    Ok(())
+}