Add Counting Inversions test

Author: LyangHiga

src/divide-and-conquer/countingInversions.test.ts

@@ -0,0 +1,8 @@
+import countingInversions from "./countingInversions";
+
+describe("Counting Inversions test", () => {
+  test("Example test", () => {
+    const A = [2, 4, 1, 3, 5];
+    expect(countingInversions(A)[1]).toBe(3);
+  });
+});

src/divide-and-conquer/countingInversions.ts

@@ -52,4 +52,4 @@ const merge = (left: number[], right: number[]): [number[], number] => {
   return [arr, counter];
 };
 
-export = sortAndCount;
+export default sortAndCount;