Complete day 5

diff --git a/src/day05.rs b/src/day05.rs
new file mode 100644 (file)
index 0000000..efbb7b2
--- /dev/null
+++ b/src/day05.rs
@@ -0,0 +1,155 @@
+use std::collections::{HashMap, HashSet};
+use std::rc::Rc;
+
+fn input() -> &'static str {
+    include_str!("../input/day05.txt")
+}
+
+type PageSet = HashSet<u8>;
+type PageRel = HashMap<u8, PageSet>;
+
+#[derive(Debug)]
+struct Page {
+    num: u8,
+    rel: Rc<PageRel>,
+}
+
+impl PartialEq for Page {
+    fn eq(&self, other: &Self) -> bool {
+        self.num == other.num
+    }
+}
+
+impl Eq for Page {}
+
+impl PartialOrd for Page {
+    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
+        Some(self.cmp(other))
+    }
+}
+
+impl Ord for Page {
+    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
+        if self == other {
+            std::cmp::Ordering::Equal
+        } else if self
+            .rel
+            .get(&self.num)
+            .unwrap_or_else(|| panic!("{:?}", self))
+            .contains(&other.num)
+        {
+            std::cmp::Ordering::Less
+        } else {
+            std::cmp::Ordering::Greater
+        }
+    }
+}
+
+fn parse(input: &str) -> Vec<Vec<Page>> {
+    let [ord, runs] = input.split("\n\n").collect::<Vec<_>>()[..] else {
+        panic!()
+    };
+
+    let mut rel = PageRel::new();
+
+    let rels: Vec<Vec<u8>> = ord
+        .split_terminator("\n")
+        .map(|s| s.split("|").map(|n| n.parse().unwrap()).collect::<Vec<_>>())
+        .collect();
+
+    for pair in rels {
+        let [l, r] = pair[..] else { panic!() };
+        rel.entry(r).or_default();
+        rel.entry(l).or_default().insert(r);
+    }
+
+    let relf = Rc::new(rel);
+
+    let pages: Vec<Vec<Page>> = runs
+        .split_terminator("\n")
+        .map(|s| {
+            s.split(",")
+                .map(|n| Page {
+                    num: n.parse().unwrap(),
+                    rel: Rc::clone(&relf),
+                })
+                .collect()
+        })
+        .collect();
+
+    pages
+}
+
+fn get_middle(run: &[Page]) -> u8 {
+    run[(run.len() + 1) / 2].num
+}
+
+pub fn part1() {
+    let pages = parse(input());
+    let n: u32 = pages
+        .iter()
+        .filter(|p| p.is_sorted())
+        .map(|p| -> u32 { get_middle(p).into() })
+        .sum();
+    println!("Day 5 Part 1: {}", n);
+}
+
+pub fn part2() {
+    let mut pages = parse(input());
+    let n: u32 = pages
+        .iter_mut()
+        .filter(|p| !p.is_sorted())
+        .map(|p| -> u32 {
+            p.sort();
+            get_middle(p).into()
+        })
+        .sum();
+    println!("Day 5 Part 2: {}", n);
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    const INPUT_STR: &str = concat!(
+        "47|53\n",
+        "97|13\n",
+        "97|61\n",
+        "97|47\n",
+        "75|29\n",
+        "61|13\n",
+        "75|53\n",
+        "29|13\n",
+        "97|29\n",
+        "53|29\n",
+        "61|53\n",
+        "97|53\n",
+        "61|29\n",
+        "47|13\n",
+        "75|47\n",
+        "97|75\n",
+        "47|61\n",
+        "75|61\n",
+        "47|29\n",
+        "75|13\n",
+        "53|13\n",
+        "\n",
+        "75,47,61,53,29\n",
+        "97,61,53,29,13\n",
+        "75,29,13\n",
+        "75,97,47,61,53\n",
+        "61,13,29\n",
+        "97,13,75,29,47\n",
+    );
+
+    #[test]
+    fn test_page_sort() {
+        let pages = parse(INPUT_STR);
+        assert!(&pages[0].is_sorted());
+        assert!(&pages[1].is_sorted());
+        assert!(&pages[2].is_sorted());
+        assert!(!&pages[3].is_sorted());
+        assert!(!&pages[4].is_sorted());
+        assert!(!&pages[5].is_sorted());
+    }
+}

diff --git a/src/main.rs b/src/main.rs
index ffc622c7bfcc4ae580b204a6e6d8309baaa40b7f..c57bf00eab0bdf10bbc7c05ba68104b385bfa72d 100644 (file)
--- a/src/main.rs
+++ b/src/main.rs
@@ -2,7 +2,7 @@ pub mod day01;
 pub mod day02;
 pub mod day03;
 pub mod day04;
-// pub mod day05;
+pub mod day05;
 // pub mod day06;
 // pub mod day07;
 // pub mod day08;
@@ -26,12 +26,12 @@ pub mod day04;
 
 type Part = fn();
 
-const DAYS: [(Part, Part); 4] = [
+const DAYS: [(Part, Part); 5] = [
     (day01::part1 as fn(), day01::part2 as fn()),
     (day02::part1 as fn(), day02::part2 as fn()),
     (day03::part1 as fn(), day03::part2 as fn()),
     (day04::part1 as fn(), day04::part2 as fn()),
-    // (day05::part1 as fn(), day05::part2 as fn()),
+    (day05::part1 as fn(), day05::part2 as fn()),
     // (day06::part1 as fn(), day06::part2 as fn()),
     // (day07::part1 as fn(), day07::part2 as fn()),
     // (day08::part1 as fn(), day08::part2 as fn()),