2022 day3/rust: add solution

2022/day3/rust/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "rust_2022_03"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

2022/day3/rust/src/main.rs

@@ -0,0 +1,44 @@
+use std::{
+    collections::HashSet,
+    io::{stdin, Read},
+};
+
+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!(),
+    }
+}
+
+fn main() {
+    let mut data = String::new();
+    stdin().read_to_string(&mut data).unwrap();
+
+    let mut sum = 0;
+    for line in data.lines() {
+        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);
+    }
+
+    println!("{}", sum);
+
+    let mut sum = 0;
+    for lines in data.lines().collect::<Vec<_>>().chunks(3) {
+        let common = lines
+            .iter()
+            .map(|line| line.chars().collect::<HashSet<_>>())
+            .reduce(|l, r| &l & &r)
+            .unwrap();
+        assert_eq!(common.len(), 1);
+
+        sum += item_priority(common.into_iter().next().unwrap());
+    }
+    println!("{}", sum);
+}

Cargo.lock

@@ -469,6 +469,10 @@ version = "0.1.0"
 name = "rust_2022_02"
 version = "0.1.0"
 
+[[package]]
+name = "rust_2022_03"
+version = "0.1.0"
+
 [[package]]
 name = "ryu"
 version = "1.0.11"

Cargo.toml

@@ -11,4 +11,5 @@ members = [
 	"2021/day22/rust",
 	"2022/day1/rust",
 	"2022/day2/rust",
+	"2022/day3/rust",
 ]