From b2744f9a7bcceb036cc138a836723357e21ae1f7 Mon Sep 17 00:00:00 2001
From: Ishan Jain <ishan.jain@zscaler.com>
Date: Fri, 20 Dec 2024 12:35:45 +0530
Subject: [PATCH] optimized day 19

---
 src/day19/1.rs | 23 +++++++++++++++++------
 src/day19/2.rs | 30 ++++++++++++++++++++++--------
 2 files changed, 39 insertions(+), 14 deletions(-)

diff --git a/src/day19/1.rs b/src/day19/1.rs
index 73ed073..ab740d4 100644
--- a/src/day19/1.rs
+++ b/src/day19/1.rs
@@ -19,24 +19,23 @@ bbrgwb",
 
 pub fn run(input: &str) -> i64 {
     let (towels, to_make) = input.split_once("\n\n").unwrap();
-    let towels = towels.split(", ").map(|x| x.bytes().collect::<Vec<u8>>()).collect::<FxHashSet<Vec<u8>>>();
-    let to_make = to_make.lines().map(|x| x.bytes().collect::<Vec<u8>>());
+    let towels = towels.split(", ").map(|x| remap(x.as_bytes())).collect::<FxHashSet<u64>>();
 
     let mut count = 0;
-    for pattern in to_make {
-        count += test(&towels, &pattern) as i64;
+    for pattern in to_make.lines() {
+        count += test(&towels, pattern.as_bytes()) as i64;
     }
     count
 }
 
-fn test(towels: &FxHashSet<Vec<u8>>, pattern: &[u8]) -> bool {
+fn test(towels: &FxHashSet<u64>, pattern: &[u8]) -> bool {
     let n = pattern.len();
     let mut dp = vec![false; n + 1];
     dp[0] = true;
 
     for i in 1..n+1 {
         for j in 0..i {
-            if dp[j] && towels.contains(&pattern[j..i]) {
+            if dp[j] && (i - j <= 8 && towels.contains(&remap(&pattern[j..i]))) {
                 dp[i] = true;
                 break;
             }
@@ -46,6 +45,18 @@ fn test(towels: &FxHashSet<Vec<u8>>, pattern: &[u8]) -> bool {
     dp[n]
 }
 
+#[inline]
+const fn remap(n: &[u8]) -> u64 {
+    let mut out = 0;
+    let mut i = 0;
+    while i < n.len() {
+        out <<= 8;
+        out |= n[i as usize] as u64;
+        i += 1;
+    }
+    out
+}
+
 fn main() {
     for input in INPUTS.iter() {
         println!("answer = {}", run(input));
diff --git a/src/day19/2.rs b/src/day19/2.rs
index 878ccb7..17048b0 100644
--- a/src/day19/2.rs
+++ b/src/day19/2.rs
@@ -19,25 +19,27 @@ bbrgwb",
 
 pub fn run(input: &str) -> i64 {
     let (towels, to_make) = input.split_once("\n\n").unwrap();
-    let towels = towels.split(", ").map(|x| x.bytes().collect::<Vec<u8>>()).collect::<FxHashSet<Vec<u8>>>();
-    let to_make = to_make.lines().map(|x| x.bytes().collect::<Vec<u8>>());
+    let towels = towels.split(", ").map(|x| remap(x.as_bytes())).collect::<FxHashSet<u64>>();
 
     let mut count = 0;
-    for pattern in to_make {
-        let sum = test(&towels, &pattern);
-        count += sum;
+    for pattern in to_make.lines() {
+        count += test(&towels, pattern.as_bytes());
     }
     count
 }
 
-fn test(towels: &FxHashSet<Vec<u8>>, pattern: &[u8]) -> i64 {
+fn test(towels: &FxHashSet<u64>, pattern: &[u8]) -> i64 {
     let n = pattern.len();
     let mut dp = vec![0; n + 1];
     dp[0] = 1; // only 1 way to make an empty string
 
     for i in 1..n+1 {
         for j in 0..i {
-            if towels.contains(&pattern[j..i]) {
+            // no word bigger than 8 chars
+            if i - j > 8 {
+                continue;
+            }
+            if towels.contains(&remap(&pattern[j..i])) {
                 dp[i] += dp[j];
             }
         }
@@ -46,6 +48,18 @@ fn test(towels: &FxHashSet<Vec<u8>>, pattern: &[u8]) -> i64 {
     dp[n]
 }
 
+#[inline]
+const fn remap(n: &[u8]) -> u64 {
+    let mut out = 0;
+    let mut i = 0;
+    while i < n.len() {
+        out <<= 8;
+        out |= n[i as usize] as u64;
+        i += 1;
+    }
+    out
+}
+
 fn main() {
     for input in INPUTS.iter() {
         println!("answer = {}", run(input));
@@ -53,7 +67,7 @@ fn main() {
 }
 
 #[bench]
-fn part1(b: &mut test::Bencher) {
+fn part2(b: &mut test::Bencher) {
     b.iter(|| {
         let v = run(INPUTS[1]);
         test::black_box(v);