add day 4

2026-06-27 14:01:46 +02:00
parent 2237d672bd
commit fd7d6f582a
5 changed files with 1123 additions and 0 deletions
@@ -0,0 +1,114 @@
+use std::collections::HashMap;
+
+#[cfg(debug_assertions)]
+const FILENAME: &str = "example.txt";
+#[cfg(not(debug_assertions))]
+const FILENAME: &str = "input.txt";
+
+fn main() {
+    let binding = std::fs::read_to_string(FILENAME).unwrap();
+    let mut data: Vec<_> = binding.lines().map(Room::parse).collect();
+
+    part1(&data);
+    part2(&mut data);
+}
+
+fn part2(data: &mut [Room]) {
+    for room in data {
+        room.shift();
+        if room.get_name().contains("northpole") {
+            println!("{}", room.id);
+            break;
+        }
+    }
+}
+
+fn part1(data: &[Room]) {
+    let x = data
+        .iter()
+        .filter(|r| r.is_valid())
+        .map(|r| r.id)
+        .sum::<u64>();
+
+    println!("{x}");
+}
+
+#[derive(Debug)]
+struct Room {
+    name: Vec<char>,
+    pub id: u64,
+    checksum: Vec<char>,
+}
+
+impl Room {
+    fn shift(&mut self) {
+        for _ in 0..self.id {
+            self.name.iter_mut().for_each(|c| {
+                if c.is_ascii_lowercase() {
+                    *c = (((((*c as u8) + 1) - 97) % 26) + 97) as char;
+                }
+            });
+        }
+    }
+
+    fn get_name(&self) -> String {
+        self.name.iter().collect()
+    }
+
+    fn parse(s: &str) -> Self {
+        let checksum = s
+            .split('[')
+            .next_back()
+            .unwrap()
+            .split(']')
+            .next()
+            .unwrap()
+            .chars()
+            .collect();
+
+        let id = s
+            .chars()
+            .skip_while(|c| !c.is_ascii_digit())
+            .take(3)
+            .collect::<String>()
+            .parse()
+            .unwrap();
+
+        let mut name: Vec<char> = s.chars().rev().skip_while(|c| *c != '-').skip(1).collect();
+        name.reverse();
+
+        Self { name, id, checksum }
+    }
+
+    fn is_valid(&self) -> bool {
+        let mut letters: Vec<_> = self
+            .name
+            .iter()
+            .filter(|c| c.is_ascii_lowercase())
+            .collect();
+
+        letters.sort();
+
+        let mut count = HashMap::new();
+
+        for c in letters {
+            count
+                .entry(c)
+                .and_modify(|counter| *counter += 1)
+                .or_insert(1);
+        }
+
+        let mut count_vec: Vec<_> = count.into_iter().map(|(c, i)| (*c, i)).collect();
+
+        count_vec.sort_by(|a, b| b.1.cmp(&a.1).then(a.0.cmp(&b.0)));
+
+        let most_common_letters_correct_count = count_vec
+            .into_iter()
+            .map(|(c, _)| c)
+            .zip(&self.checksum)
+            .filter(|(l, r)| l == *r)
+            .count();
+
+        most_common_letters_correct_count == 5
+    }
+}