From b00e1fa769e1df7c497e2aa9c9545fb20ab81a63 Mon Sep 17 00:00:00 2001
From: Xavier Morel <morelx42@gmail.com>
Date: Sun, 22 Dec 2024 11:40:37 +0100
Subject: [PATCH] feat: day 19

---
 README.md            |   3 +-
 data/examples/19.txt |  10 ++++
 src/bin/19.rs        | 127 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 139 insertions(+), 1 deletion(-)
 create mode 100644 data/examples/19.txt
 create mode 100644 src/bin/19.rs

diff --git a/README.md b/README.md
index 5365520..15ab7d9 100644
--- a/README.md
+++ b/README.md
@@ -49,8 +49,9 @@ Solutions for [Advent of Code](https://adventofcode.com/) in [Rust](https://www.
 | [Day 16](./src/bin/16.rs) | `-` | `-` |
 | [Day 17](./src/bin/17.rs) | `1.5ms` | `-` |
 | [Day 18](./src/bin/18.rs) | `2.1ms` | `5.0ms` |
+| [Day 19](./src/bin/19.rs) | `21.1ms` | `707.2ms` |
 
-**Total: 13275.60ms**
+**Total: 14003.90ms**
 <!--- benchmarking table --->
 
 ---
diff --git a/data/examples/19.txt b/data/examples/19.txt
new file mode 100644
index 0000000..29648be
--- /dev/null
+++ b/data/examples/19.txt
@@ -0,0 +1,10 @@
+r, wr, b, g, bwu, rb, gb, br
+
+brwrr
+bggr
+gbbr
+rrbgbr
+ubwu
+bwurrg
+brgr
+bbrgwb
diff --git a/src/bin/19.rs b/src/bin/19.rs
new file mode 100644
index 0000000..1dcc588
--- /dev/null
+++ b/src/bin/19.rs
@@ -0,0 +1,127 @@
+advent_of_code::solution!(19);
+
+use std::collections::HashMap;
+
+fn is_possible(pat: String, towels: &Vec<String>) -> bool {
+    if towels.contains(&pat) {
+        return true;
+    }
+    for towel in towels {
+        if pat.starts_with(towel) {
+            let sub_possible = is_possible((pat[towel.len()..]).to_owned(), towels);
+            if sub_possible {
+                return true;
+            }
+        }
+    }
+
+    false
+}
+
+#[derive(Debug)]
+struct State {
+    towels: Vec<String>,
+    simplified: Vec<String>,
+    patterns: Vec<String>,
+    possible_cache: HashMap<String, usize>,
+}
+
+fn simplified_towels(towels: Vec<String>) -> Vec<String> {
+    let mut res = Vec::new();
+    for t in &towels {
+        let remaining: Vec<String> = towels.clone().into_iter().filter(|t2| t2 != t).collect();
+        if t.len() == 1 || !is_possible(t.clone(), &remaining) {
+            res.push(t.clone());
+        }
+    }
+    res
+}
+
+impl TryFrom<&str> for State {
+    type Error = ();
+    fn try_from(input: &str) -> Result<State, Self::Error> {
+        let mut input: Vec<&str> = input.lines().collect();
+        if input.len() < 3 {
+            return Err(());
+        }
+        let mut towels: Vec<String> = input.remove(0).split(", ").map(String::from).collect();
+        towels.sort_by_key(|t| (t.len(), t.clone()));
+        input.remove(0);
+        Ok(Self {
+            patterns: input.into_iter().map(|s| s.to_owned()).collect(),
+            simplified: simplified_towels(towels.clone()),
+            towels,
+            possible_cache: HashMap::new(),
+        })
+    }
+}
+
+impl State {
+    fn is_possible(&self, pat: String) -> bool {
+        is_possible(pat, &self.simplified)
+    }
+
+    fn nb_possible(&mut self, pat: String) -> usize {
+        if let Some(cached) = self.possible_cache.get(&pat) {
+            return *cached;
+        }
+        if pat.is_empty() {
+            self.possible_cache.insert(pat, 1);
+            return 1;
+        }
+        let mut res = 0;
+        for towel in &self.towels.clone() {
+            if pat.starts_with(towel) {
+                res += self.nb_possible((pat[towel.len()..]).to_owned());
+            }
+        }
+        self.possible_cache.insert(pat, res);
+        res
+    }
+
+    fn get_possible_patterns_count(&self) -> usize {
+        self.patterns
+            .iter()
+            .filter(|p| self.is_possible(p.to_string()))
+            .count()
+    }
+
+    fn get_nb_possible_configurations(&mut self) -> usize {
+        self.patterns
+            .clone()
+            .into_iter()
+            .map(|p| self.nb_possible(p.to_string()))
+            .sum::<usize>()
+    }
+}
+
+pub fn part_one(input: &str) -> Option<usize> {
+    State::try_from(input)
+        .ok()?
+        .get_possible_patterns_count()
+        .into()
+}
+
+pub fn part_two(input: &str) -> Option<usize> {
+    State::try_from(input)
+        .ok()?
+        .get_nb_possible_configurations()
+        .into()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(6));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(16));
+    }
+}