Add caching back in

day_07/src/equation.rs

@@ -55,7 +55,7 @@ impl Equation {
             match op {
                 Op::Multiply => accumulator *= self.components[i + 1],
                 Op::Add => accumulator += self.components[i + 1],
-                Op::CONCAT => {
+                Op::Concat => {
                     let accumulator_string = format!("{}", accumulator);
                     let component_string = format!("{}", self.components[i + 1]);
                     accumulator = (accumulator_string + &component_string).parse().unwrap();
@@ -82,7 +82,7 @@ impl Equation {
 
     pub fn solvable_multiply_add_concat(&self) -> bool {
         let op_combinations = create_permutations(
-            HashSet::from([Op::Add, Op::Multiply, Op::CONCAT]),
+            HashSet::from([Op::Add, Op::Multiply, Op::Concat]),
             self.components.len() - 1,
         );
 

day_07/src/equation/operator_set.rs

@@ -4,27 +4,42 @@ use std::collections::HashSet;
 pub enum Op {
     Multiply,
     Add,
-    CONCAT,
+    Concat,
 }
 
-// use std::collections::HashMap;
-// use std::sync::{LazyLock, Mutex};
+#[derive(Debug, Clone, Hash, PartialEq, Eq)]
+struct PermutationCacheKey {
+    size: usize,
+    set: Vec<Op>,
+}
 
-// type OperatorCache = HashMap<usize, HashSet<Vec<Op>>>;
+impl PermutationCacheKey {
+    fn new(size: usize, set: &HashSet<Op>) -> PermutationCacheKey {
+        PermutationCacheKey {
+            size,
+            set: set.iter().cloned().collect(),
+        }
+    }
+}
 
-// static OPERATOR_SET_CACHE: LazyLock<Mutex<OperatorCache>> =
-//     LazyLock::new(|| Mutex::new(HashMap::new()));
+use std::collections::HashMap;
+use std::sync::{LazyLock, Mutex};
 
-// fn check_operator_set_cache(cache_key: usize) -> Option<HashSet<Vec<Op>>> {
-//     OPERATOR_SET_CACHE.lock().unwrap().get(&cache_key).cloned()
-// }
+type OperatorCache = HashMap<PermutationCacheKey, HashSet<Vec<Op>>>;
 
-// fn store_operator_set_in_cache(cache_key: usize, cache_value: HashSet<Vec<Op>>) {
-//     OPERATOR_SET_CACHE
-//         .lock()
-//         .unwrap()
-//         .insert(cache_key, cache_value);
-// }
+static OPERATOR_SET_CACHE: LazyLock<Mutex<OperatorCache>> =
+    LazyLock::new(|| Mutex::new(HashMap::new()));
+
+fn check_operator_set_cache(cache_key: &PermutationCacheKey) -> Option<HashSet<Vec<Op>>> {
+    OPERATOR_SET_CACHE.lock().unwrap().get(cache_key).cloned()
+}
+
+fn store_operator_set_in_cache(cache_key: PermutationCacheKey, cache_value: HashSet<Vec<Op>>) {
+    OPERATOR_SET_CACHE
+        .lock()
+        .unwrap()
+        .insert(cache_key, cache_value);
+}
 
 // fn create_operator_set_recurse(
 //     operators_permutation_set: &mut HashSet<Vec<Op>>,
@@ -79,7 +94,11 @@ fn create_permutations_recurse(
 }
 
 pub fn create_permutations(set: HashSet<Op>, len: usize) -> HashSet<Vec<Op>> {
+    if let Some(cached_value) = check_operator_set_cache(&PermutationCacheKey::new(len, &set)) {
+        return cached_value;
+    }
     let mut permutations = HashSet::new();
     create_permutations_recurse(&set, len, &mut permutations, vec![]);
+    store_operator_set_in_cache(PermutationCacheKey::new(len, &set), permutations.clone());
     permutations
 }