From fbf68e490f98735897b6ef28f047e1b259b40eab Mon Sep 17 00:00:00 2001
From: Walle Cyril <cyril.walle@protonmail.com>
Date: Sat, 22 Jun 2019 15:39:41 +0200
Subject: [PATCH 1/2] fix: return empty set when either is empty

---
 src/algorithms/sets/cartesian-product/cartesianProduct.js | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/algorithms/sets/cartesian-product/cartesianProduct.js b/src/algorithms/sets/cartesian-product/cartesianProduct.js
index 14924fae..93f05f18 100644
--- a/src/algorithms/sets/cartesian-product/cartesianProduct.js
+++ b/src/algorithms/sets/cartesian-product/cartesianProduct.js
@@ -5,14 +5,17 @@
  * @return {*[]}
  */
 export default function cartesianProduct(setA, setB) {
-  // Check if input sets are not empty.
+  // Check if input sets are not non-arrays.
   // Otherwise return null since we can't generate Cartesian Product out of them.
-  if (!setA || !setB || !setA.length || !setB.length) {
+  if (!setA || !setB) {
     return null;
   }
 
   // Init product set.
   const product = [];
+  if (!setA.length || !setB.length) {
+    return product;
+  }
 
   // Now, let's go through all elements of a first and second set and form all possible pairs.
   for (let indexA = 0; indexA < setA.length; indexA += 1) {

From ecdc7bd1723bd8f70764c5f1c19728b75c493405 Mon Sep 17 00:00:00 2001
From: Walle Cyril <cyril.walle@protonmail.com>
Date: Sat, 22 Jun 2019 17:01:03 +0200
Subject: [PATCH 2/2] test cartesian product

---
 .../cartesian-product/__test__/cartesianProduct.test.js   | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/algorithms/sets/cartesian-product/__test__/cartesianProduct.test.js b/src/algorithms/sets/cartesian-product/__test__/cartesianProduct.test.js
index f9154fa2..32ae3479 100644
--- a/src/algorithms/sets/cartesian-product/__test__/cartesianProduct.test.js
+++ b/src/algorithms/sets/cartesian-product/__test__/cartesianProduct.test.js
@@ -16,4 +16,12 @@ describe('cartesianProduct', () => {
     expect(product1).toEqual([[1, 1]]);
     expect(product2).toEqual([[1, 3], [1, 5], [2, 3], [2, 5]]);
   });
+
+  it('should return an empty set if one or both of the source is empty', () => {
+    const product1 = cartesianProduct([], [1, 2, 3]);
+    const product2 = cartesianProduct([], []);
+
+    expect(product1).toEqual([]);
+    expect(product2).toEqual([]);
+  });
 });