Inversion count done!

Pretty challenging but a lot of fun and very satisfying. Decided to
implement MergeSort first without worrying about inversion count, then
went from there. Lesson learned: use the debugger! :) Also passing by
reference in Java can be convenient.

1 files changed, 50 insertions, 0 deletions

diff --git a/AlgoDesignAndTechniqueEdxJava/tests/InversionCountTest.java b/AlgoDesignAndTechniqueEdxJava/tests/InversionCountTest.java
new file mode 100644
index 0000000..483cd23
--- /dev/null
+++ b/AlgoDesignAndTechniqueEdxJava/tests/InversionCountTest.java
@@ -0,0 +1,50 @@
+import static org.junit.jupiter.api.Assertions.*;
+
+import org.junit.jupiter.api.Test;
+
+class InversionCountTest {
+
+	@Test
+	void testInversionCount0() {
+		int[] a = {2, 3, 9, 2, 9};
+		assertEquals(2, InversionCount.getInversionCountFromArray(a));
+	}
+
+	@Test
+	void testInversionCount1() {
+		int[] a = {1, 1, 1, 1, 1};
+		assertEquals(0, InversionCount.getInversionCountFromArray(a));
+	}
+
+	@Test
+	void testInversionCount2() {
+		int[] a = {6, 5, 4, 3, 2, 1};
+		assertEquals(15, InversionCount.getInversionCountFromArray(a));
+	}
+
+	@Test
+	void testInversionCount3() {
+		int[] a = {1, 1, 1, 2, 1};
+		assertEquals(1, InversionCount.getInversionCountFromArray(a));
+	}
+
+	@Test
+	void testInversionCount4() {
+		int[] a = {2, 1, 1};
+		assertEquals(2, InversionCount.getInversionCountFromArray(a));
+	}
+
+	@Test
+	void testMergeSort0() {
+		int[] a = {2, 3, 9, 2, 9};
+		int[] b = {2, 2, 3, 9, 9};
+		assertArrayEquals(b, InversionCount.mergeSortArray(a));
+	}
+
+	@Test
+	void testMergeSort1() {
+		int[] a = {5, 4, 3, 2, 1};
+		int[] b = {1, 2, 3, 4, 5};
+		assertArrayEquals(b, InversionCount.mergeSortArray(a));
+	}
+}