day 3

day_3/src/main.rs

@@ -1,3 +1,72 @@
-fn main() {
-    println!("Hello, world!");
+use std::{collections::HashSet, fs::read_to_string, ops::Deref};
+
+const PATH: &str = "src/input";
+
+fn value(c: char) -> u32 {
+    if c.is_ascii_lowercase() {
+        return (c as u8 - b'a' + 1) as u32;
+    } else if c.is_ascii_uppercase() {
+        return (c as u8 - b'A' + 27) as u32;
+    } else {
+        panic!()
+    }
+}
+
+fn main() {
+    part_1();
+    part_2();
+}
+
+fn to_hash(bag: Option<&str>) -> HashSet<&u8> {
+    return HashSet::from_iter(bag.expect("must be some").as_bytes().iter());
+}
+
+fn part_2() {
+    let binding = read_to_string(PATH).expect("Error reading file");
+    let mut data = binding.split_ascii_whitespace().into_iter().peekable();
+    let mut priority_sum: u32 = 0;
+    while data.peek().is_some() {
+        let test = **to_hash(data.next())
+            .intersection(&to_hash(data.next()))
+            .cloned()
+            .collect::<HashSet<&u8>>()
+            .intersection(&to_hash(data.next()))
+            .last()
+            .expect("expect") as char;
+        priority_sum += value(test)
+    }
+    println!("PART 2 {}", priority_sum);
+}
+
+fn part_1() {
+    let data = read_to_string(PATH).expect("Error reading file");
+    let mut priority_sum: u32 = 0;
+    data.split_ascii_whitespace().for_each(|line| {
+        // Expect only bytes.
+        let first_bag = line.as_bytes().get(0..line.len() / 2).expect("line").iter();
+        let second_bag = line
+            .as_bytes()
+            .get(line.len() / 2..line.len())
+            .expect("line")
+            .iter();
+        let first_set: HashSet<&u8> = HashSet::from_iter(first_bag);
+        let second_set: HashSet<&u8> = HashSet::from_iter(second_bag);
+        let common = *first_set
+            .intersection(&second_set)
+            .last()
+            .unwrap_or(&&b'?')
+            .deref() as char;
+
+        priority_sum += value(common);
+
+        // println!(
+        //     "{} | {} => {} {}",
+        //     std::str::from_utf8(line.as_bytes().get(0..line.len() / 2).unwrap()).unwrap(),
+        //     std::str::from_utf8(line.as_bytes().get(line.len() / 2..line.len()).unwrap()).unwrap(),
+        //     common,
+        //     value(common)
+        // );
+    });
+
+    println!("PART 1 {}", priority_sum);
 }