From de9edd71ccb7ec5919a64a70afe3592daf94617d Mon Sep 17 00:00:00 2001
From: Bearmine <bearmine@bearmine.com>
Date: Mon, 16 Jun 2025 11:54:01 -0500
Subject: [PATCH] Cache operator sets

---
 day_07/src/equation/operator_set.rs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/day_07/src/equation/operator_set.rs b/day_07/src/equation/operator_set.rs
index d8b6815..c291157 100644
--- a/day_07/src/equation/operator_set.rs
+++ b/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
 }