day 19

data/examples/19.txt

@@ -0,0 +1,10 @@
+r, wr, b, g, bwu, rb, gb, br
+
+brwrr
+bggr
+gbbr
+rrbgbr
+ubwu
+bwurrg
+brgr
+bbrgwb

src/bin/19.rs

@@ -0,0 +1,105 @@
+use std::collections::HashMap;
+
+use itertools::Itertools;
+
+advent_of_code::solution!(19);
+
+pub fn part_one(input: &str) -> Option<u32> {
+    let (towels_str, wanted_str) = input.split_once("\n\n").unwrap();
+    let towels = towels_str.split(",").map(|s| s.trim()).collect_vec();
+    let wanted = wanted_str.lines().collect_vec();
+
+    let mut results = vec![];
+
+    let mut lookup: HashMap<String, bool> = HashMap::new();
+    for w in wanted {
+        let res = dfs(w, &towels, &mut lookup);
+        if res {
+            results.push(res);
+        };
+    }
+
+    Some(results.len() as u32)
+}
+
+fn dfs(wanted: &str, towels: &[&str], lookup: &mut HashMap<String, bool>) -> bool {
+    // Check Lookup
+    if let Some(cached) = lookup.get(&wanted.to_string()) {
+        return cached.to_owned();
+    };
+
+    let mut res = false;
+    for t in towels {
+        if let Some(stripped) = wanted.strip_prefix(t) {
+            if stripped.is_empty() {
+                res = true
+            } else {
+                let has_solution = dfs(stripped, towels, lookup);
+                if has_solution {
+                    res = true
+                }
+            }
+        } else {
+            continue;
+        }
+    }
+
+    lookup.insert(wanted.to_owned(), res);
+    res
+}
+
+pub fn part_two(input: &str) -> Option<u64> {
+    let (towels_str, wanted_str) = input.split_once("\n\n").unwrap();
+    let towels = towels_str.split(",").map(|s| s.trim()).collect_vec();
+    let wanted = wanted_str.lines().collect_vec();
+
+    let mut results: Vec<u64> = vec![];
+
+    let mut lookup: HashMap<String, u64> = HashMap::new();
+    for w in wanted {
+        let res = dfs2(w, &towels, &mut lookup);
+        results.push(res);
+    }
+
+    Some(results.iter().sum())
+}
+
+fn dfs2(wanted: &str, towels: &[&str], lookup: &mut HashMap<String, u64>) -> u64 {
+    // Check Lookup
+    if let Some(cached) = lookup.get(&wanted.to_string()) {
+        return cached.to_owned();
+    };
+
+    let mut res = 0;
+    for t in towels {
+        if let Some(stripped) = wanted.strip_prefix(t) {
+            if stripped.is_empty() {
+                res += 1
+            } else {
+                res += dfs2(stripped, towels, lookup);
+            }
+        } else {
+            continue;
+        }
+    }
+
+    lookup.insert(wanted.to_owned(), res);
+    res
+}
+
+#[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, None);
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, None);
+    }
+}