Cache operator sets

day_07/src/equation/operator_set.rs

@@ -1,4 +1,11 @@
+use std::collections::HashMap;
 use std::collections::HashSet;
+use std::sync::{LazyLock, Mutex};
+
+type OperatorCache = HashMap<usize, HashSet<Vec<bool>>>;
+
+static OPERATOR_SET_CACHE: LazyLock<Mutex<OperatorCache>> =
+    LazyLock::new(|| Mutex::new(HashMap::new()));
 
 fn create_operator_set_recurse(
     operators_permutation_set: &mut HashSet<Vec<bool>>,
@@ -20,7 +27,20 @@ fn create_operator_set_recurse(
 }
 
 pub fn create_operator_set(num_of_operators: usize) -> HashSet<Vec<bool>> {
+    {
+        // Check cache
+        if let Some(cached_value) = OPERATOR_SET_CACHE.lock().unwrap().get(&num_of_operators) {
+            return cached_value.clone();
+        }
+    }
     let mut operator_sets: HashSet<Vec<bool>> = HashSet::new();
     create_operator_set_recurse(&mut operator_sets, vec![false; num_of_operators]);
+    {
+        // Store value in cache
+        OPERATOR_SET_CACHE
+            .lock()
+            .unwrap()
+            .insert(num_of_operators, operator_sets.clone());
+    }
     operator_sets
 }