y2024d19

y2024/src/bin/d19.rs

@@ -0,0 +1,27 @@
+use std::{fs, time::Instant};
+
+use utils::time::get_elapsed_string;
+use y2024::days::d19;
+
+fn main() {
+    let now = Instant::now();
+    println!("Part 1:");
+    part1();
+    println!("Ran in {}", get_elapsed_string(now.elapsed()));
+    let now = Instant::now();
+    println!("Part 2:");
+    part2();
+    println!("Ran in {}", get_elapsed_string(now.elapsed()));
+}
+
+fn part1() {
+    let root = env!("CARGO_MANIFEST_DIR");
+    let content = fs::read_to_string(format!("{root}/resources/19_input.txt")).unwrap();
+    println!("{}", d19::process_part1(&content));
+}
+
+fn part2() {
+    let root = env!("CARGO_MANIFEST_DIR");
+    let content = fs::read_to_string(format!("{root}/resources/19_input.txt")).unwrap();
+    println!("{}", d19::process_part2(&content));
+}

y2024/src/days/d19.rs

@@ -0,0 +1,96 @@
+use std::collections::HashMap;
+
+use itertools::Itertools;
+
+pub fn process_part1(input: &str) -> u64 {
+    let (patterns, designs) = input.split_once("\n\n").unwrap();
+    let patterns = patterns.split(", ").collect_vec();
+    designs
+        .lines()
+        .map(|design| {
+            if possible_design(design, &patterns) {
+                1
+            } else {
+                0
+            }
+        })
+        .sum()
+}
+
+fn possible_design(design: &str, patterns: &[&str]) -> bool {
+    for pattern in patterns {
+        if design.starts_with(pattern) && design.len() == pattern.len() {
+            return true;
+        } else if design.starts_with(pattern) {
+            if let Some(stripped) = design.strip_prefix(pattern) {
+                if possible_design(stripped, patterns) {
+                    return true;
+                }
+            }
+        }
+    }
+    false
+}
+
+fn possible_designs(design: &str, patterns: &[&str], memo: &mut HashMap<String, u64>) -> u64 {
+    if design.is_empty() {
+        return 0;
+    }
+    let mut num_possible_designs = 0;
+    if let Some(count) = memo.get(design) {
+        return *count;
+    }
+    for pattern in patterns {
+        if design == *pattern {
+            memo.insert(design.to_string(), 1);
+            num_possible_designs += 1;
+        }
+        if design.starts_with(pattern) {
+            if let Some(stripped) = design.strip_prefix(pattern) {
+                let for_stripped = possible_designs(stripped, patterns, memo);
+                memo.entry(stripped.to_string()).or_insert(for_stripped);
+                num_possible_designs += for_stripped;
+            }
+        }
+    }
+    memo.insert(design.to_string(), num_possible_designs);
+    num_possible_designs
+}
+
+pub fn process_part2(input: &str) -> u64 {
+    let (patterns, designs) = input.split_once("\n\n").unwrap();
+    let patterns = patterns.split(", ").collect_vec();
+    let mut memo = HashMap::new();
+    designs
+        .lines()
+        .map(|design| possible_designs(design, &patterns, &mut memo))
+        .sum()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const INPUT: &str = "r, wr, b, g, bwu, rb, gb, br
+
+brwrr
+bggr
+gbbr
+rrbgbr
+ubwu
+bwurrg
+brgr
+bbrgwb";
+
+    #[test]
+    fn part1() {
+        let result = process_part1(INPUT);
+        assert_eq!(result, 6);
+    }
+
+    #[test]
+    fn part2() {
+        let result = process_part2(INPUT);
+        assert_eq!(result, 16);
+    }
+}

y2024/src/days/mod.rs

@@ -25,3 +25,5 @@ pub mod d16;
 pub mod d17;
 
 pub mod d18;
+
+pub mod d19;