day 3

day3/src/main.rs

@@ -0,0 +1,73 @@
+use std::collections::HashSet;
+
+fn char_to_prio(c: char) -> u64 {
+    if c.is_ascii_uppercase() {
+        let ci = c as u8;
+        return u64::from(ci - b'A' + 27);
+    }
+    else if c.is_ascii_lowercase() {
+        let ci = c as u8;
+        return u64::from(ci - b'a' + 1);
+    }
+
+    0
+}
+
+fn main() {
+    const INPUT: &str = include_str!("../input.txt");
+
+    let input = INPUT.lines();
+    let mut priority_sum: u64 = 0;
+    for line in input {
+        let compartments = line.clone().split_at(line.len() / 2);
+
+        let items: HashSet<char> = HashSet::from_iter(compartments.0.chars());
+        let mut new_items: HashSet<char> = HashSet::new();
+        
+        for c in compartments.1.chars() {
+            if new_items.insert(c) && items.contains(&c) {
+                priority_sum += char_to_prio(c);
+            }
+        }
+    }
+
+    println!("Priority sum: {}", priority_sum);
+
+    let mut input = INPUT.lines().peekable();
+    priority_sum = 0;
+    while input.peek().is_some() {
+        let lines = [input.next().unwrap().clone(), input.next().unwrap().clone(), input.next().unwrap().clone()];
+
+        for c in b'A'..=b'Z' {
+            let c = c as char;
+            let mut count: u8 = 0;
+
+            for line in lines {
+                if line.chars().any(|x| x == c) {
+                    count += 1;
+                }
+            }
+
+            if count == 3 {
+                priority_sum += char_to_prio(c);
+                break;
+            }
+
+            count = 0;
+            let c = c.to_lowercase().next().unwrap();
+
+            for line in lines {
+                if line.chars().any(|x| x == c) {
+                    count += 1;
+                }
+            }
+
+            if count == 3 {
+                priority_sum += char_to_prio(c);
+                break;
+            }
+        }
+    }
+
+    println!("Priority sum: {}", priority_sum);
+}