Added cartesianProduct.js

Author: xinzhe822

Maths/CartesianProduct.js

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+/**
+ * @function cartesianProduct
+ * @description Generate Cartesian Product of Two Sets.
+ * @param {*[]} setA -First set
+ * @param {*[]} setB -Second set
+ * @return {*[]} -Cartesian Product of setA and setB
+ */
+const cartesianProduct = (setA, setB) => {
+  // Check if input sets are not empty.
+  if (!setA || !setB || !setA.length || !setB.length) {
+    return null;
+  }
+  const product = [];
+
+  for (let indexA = 0; indexA < setA.length; indexA += 1) {
+    for (let indexB = 0; indexB < setB.length; indexB += 1) {
+      product.push([setA[indexA], setB[indexB]]);
+    }
+  }
+
+  return product
+}
+
+export { cartesianProduct }

Maths/test/CartesianProduct.test.js

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+import {cartesianProduct} from '../cartesianProduct';
+
+describe('cartesianProduct', () => {
+  it('should return null if not enough info for calculation', () => {
+    const product1 = cartesianProduct([1], null)
+    const product2 = cartesianProduct([], null)
+
+    expect(product1).toBeNull()
+    expect(product2).toBeNull()
+  })
+
+  it('should calculate the product of two sets', () => {
+    const product1 = cartesianProduct([1], [1])
+    const product2 = cartesianProduct([1, 2], [3, 5])
+
+    expect(product1).toEqual([[1, 1]]);
+    expect(product2).toEqual([[1, 3], [1, 5], [2, 3], [2, 5]])
+  })
+})