Added early abort if there are too many damaged springs in a row

2023/src/bin/day12.rs

@@ -1,5 +1,8 @@
 #![feature(test)]
-use std::{collections::{HashMap, hash_map::DefaultHasher}, hash::{Hash, Hasher}};
+use std::{
+    collections::{hash_map::DefaultHasher, HashMap},
+    hash::{Hash, Hasher},
+};
 
 use anyhow::Result;
 use aoc::Solver;
@@ -76,7 +79,12 @@ impl std::fmt::Display for Spring {
 }
 
 // The cache is optional as is slows down part1 by a lot
-fn count_valid(springs: &mut [Spring], list: &[usize], damaged_chain: usize, cache: &mut Option<&mut Cache>) -> usize {
+fn count_valid(
+    springs: &mut [Spring],
+    list: &[usize],
+    damaged_chain: usize,
+    cache: &mut Option<&mut Cache>,
+) -> usize {
     let hash = if let Some(cache) = cache {
         // Calculate the hash manually, otherwise we end up with weird borrows or we have to clone
         // (which is slow)
@@ -97,7 +105,12 @@ fn count_valid(springs: &mut [Spring], list: &[usize], damaged_chain: usize, cac
 
     // We reached the end of the list, no further processing is possible
     let count = if list.is_empty() {
-        if springs.iter().filter(|&spring| spring == &Spring::Damaged).count() > 0 {
+        if springs
+            .iter()
+            .filter(|&spring| spring == &Spring::Damaged)
+            .count()
+            > 0
+        {
             // There are still damaged springs remaining
             0
         } else {
@@ -139,10 +152,15 @@ fn count_valid(springs: &mut [Spring], list: &[usize], damaged_chain: usize, cac
 
                 // Return the sum of both branches
                 a + b
-            },
+            }
             Spring::Damaged => {
-                // Add to the damaged chain
-                count_valid(&mut springs[1..], list, damaged_chain+1, cache)
+                if damaged_chain + 1 > list[0] {
+                    // The chain is to long
+                    0
+                } else {
+                    // Add to the damaged chain
+                    count_valid(&mut springs[1..], list, damaged_chain + 1, cache)
+                }
             }
         }
     };
@@ -194,10 +212,23 @@ impl aoc::Solver for Day {
                         .collect::<Vec<_>>(),
                 )
             })
-            .map(|(springs, list)| (
-                    [springs.clone(), vec![Spring::Unknown], springs.clone(), vec![Spring::Unknown], springs.clone(), vec![Spring::Unknown], springs.clone(), vec![Spring::Unknown], springs].concat(),
-                    [list.clone(), list.clone(), list.clone(), list.clone(), list].concat()
-            ))
+            .map(|(springs, list)| {
+                (
+                    [
+                        springs.clone(),
+                        vec![Spring::Unknown],
+                        springs.clone(),
+                        vec![Spring::Unknown],
+                        springs.clone(),
+                        vec![Spring::Unknown],
+                        springs.clone(),
+                        vec![Spring::Unknown],
+                        springs,
+                    ]
+                    .concat(),
+                    [list.clone(), list.clone(), list.clone(), list.clone(), list].concat(),
+                )
+            })
             .map(|(mut springs, list)| {
                 let mut cache = HashMap::new();
                 count_valid(&mut springs, &list, 0, &mut Some(&mut cache))