day19: complete solution

README.md

@@ -1,6 +1,6 @@
 <!-- AOC TILES BEGIN -->
 <h1 align="center">
-  2024 - 36 ⭐ - Rust
+  2024 - 38 ⭐ - Rust
 </h1>
 <a href="src/day1.rs">
   <img src=".aoc_tiles/tiles/2024/01.png" width="161px">
@@ -56,4 +56,7 @@
 <a href="src/day18.rs">
   <img src=".aoc_tiles/tiles/2024/18.png" width="161px">
 </a>
+<a href="src/day19.rs">
+  <img src=".aoc_tiles/tiles/2024/19.png" width="161px">
+</a>
 <!-- AOC TILES END -->

src/day19.rs

@@ -1,31 +1,193 @@
 use aoc_runner_derive::aoc;
+use cached::proc_macro::cached;
+use itertools::Itertools;
+use rustc_hash::{FxHashMap, FxHasher};
+use std::{
+    collections::VecDeque,
+    fmt::{Display, Write},
+};
 
-fn parse(input: &str) -> String {
+#[repr(u8)]
-    todo!()
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
+enum Stripe {
+    White = b'w',
+    Blue = b'u',
+    Black = b'b',
+    Red = b'r',
+    Green = b'g',
+}
+
+impl From<&u8> for Stripe {
+    fn from(value: &u8) -> Self {
+        match value {
+            b'w' => Self::White,
+            b'u' => Self::Blue,
+            b'b' => Self::Black,
+            b'r' => Self::Red,
+            b'g' => Self::Green,
+            _ => unimplemented!(),
+        }
+    }
+}
+
+impl Into<char> for &Stripe {
+    fn into(self) -> char {
+        let v = *self as u8;
+        v.into()
+    }
+}
+
+impl Display for Stripe {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_char(self.into())
+    }
+}
+
+#[derive(Debug)]
+struct Design {
+    stripes: Vec<Stripe>,
+}
+
+impl From<&[u8]> for Design {
+    fn from(input: &[u8]) -> Self {
+        let stripes = input.iter().map(|c| c.into()).collect();
+        Self { stripes }
+    }
+}
+
+impl Display for Design {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        for stripe in &self.stripes {
+            f.write_char(stripe.into())?;
+        }
+        Ok(())
+    }
+}
+
+#[derive(Debug)]
+struct Onsen {
+    towels: Vec<Design>,
+    designs: Vec<Design>,
+    // ways_cache: FxHashMap<&'a [Stripe], i64>
+}
+
+impl Display for Onsen {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.write_str(&self.towels.iter().join(", "))?;
+        writeln!(f)?;
+        writeln!(f)?;
+        for d in &self.designs {
+            d.fmt(f)?;
+            writeln!(f)?;
+        }
+        Ok(())
+    }
+}
+
+impl Onsen {
+    fn possible(&self, d: &[Stripe]) -> bool {
+        if d.len() == 0 {
+            return true;
+        }
+        for t in &self.towels {
+            if d.starts_with(&t.stripes) {
+                if self.possible(d.split_at(t.stripes.len()).1) {
+                    return true;
+                }
+            }
+        }
+        false
+    }
+    // Count the ways to construct a given substring
+    fn ways<'a>(&'a self, d: &'a [Stripe], mut cache: FxHashMap<&'a [Stripe], i64>) -> (FxHashMap<&'a [Stripe], i64>, i64) {
+        if d.len() == 0 {
+            // println!("ways to make {} - 0", d.iter().join(""));
+            return (cache, 1);
+        }
+        if cache.contains_key(d) {
+            let val = cache[d];
+            return (cache, val);
+        }
+
+        let mut count = 0;
+        for t in &self.towels {
+            if d.starts_with(&t.stripes) {
+                let res_count;
+                (cache, res_count) = self.ways(&d[t.stripes.len()..d.len()], cache);
+                count += res_count;
+            }
+        }
+        // println!("ways to make {} - {}", d.iter().join(""), count);
+        cache.insert(d, count);
+        (cache, count)
+    }
+    fn count_possible(&self) -> i64 {
+        self.designs
+            .iter()
+            .map(|d| self.possible(&d.stripes))
+            .filter(|p| *p)
+            .count() as i64
+    }
+    fn count_ways(&self) -> i64 {
+        self.designs.iter().map(|d| self.ways(&d.stripes, FxHashMap::default()).1).sum::<i64>()
+    }
+}
+
+fn parse(input: &str) -> Onsen {
+    let mut lines = input.lines();
+
+    let towels = lines
+        .next()
+        .unwrap()
+        .split(&[',', ' '])
+        .filter(|s| !s.is_empty())
+        .map(|s| s.as_bytes().into())
+        .collect();
+    lines.next().unwrap(); // discard empty line
+
+    let designs = lines.map(|l| l.as_bytes().into()).collect();
+
+    Onsen { towels, designs }
 }
 
 #[aoc(day19, part1)]
 fn part1(input: &str) -> i64 {
-    todo!()
+    let onsen = parse(input);
+
+    onsen.count_possible()
 }
 
 #[aoc(day19, part2)]
 fn part2(input: &str) -> i64 {
-    todo!()
+    let onsen = parse(input);
+
+    onsen.count_ways()
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
-    const EXAMPLE: &str = "";
+    const EXAMPLE: &str = "r, wr, b, g, bwu, rb, gb, br
+
+brwrr
+bggr
+gbbr
+rrbgbr
+ubwu
+bwurrg
+brgr
+bbrgwb";
+const EXAMPLE2: &str = "r, wr, b, g, bwu, rb, gb, br
+
+rrbgbr";
 
     #[test]
     fn part1_example() {
-        assert_eq!(part1(EXAMPLE), 0);
+        assert_eq!(part1(EXAMPLE), 6);
     }
 
     #[test]
     fn part2_example() {
-        assert_eq!(part2(EXAMPLE), 0);
+        assert_eq!(part2(EXAMPLE), 16);
     }
 }