Merging tables done!

Another interesting problem to solve. I gained a much better understanding
of disjoint sets (aka Union/Find) through the coding challenge. A few takeaways:
1. Writing test cases is so important. I can sink my teeth into it and
have something concrete to work on, instead of wasting time beating around the bush;
2. Modify starter code to make it testable, if it's not easy to test to
begin with;
3. Get started early, so I can use my "sleep on it" technique. It really
improves understanding!
4. I'm slightly bothered by the fact that I don't have a test case to catch
the issue with grader test case 8. I looked at the code and added line 61
which enabled me to pass the grader.

1 files changed, 83 insertions, 0 deletions

diff --git a/src/test/MergingTablesTest.java b/src/test/MergingTablesTest.java
new file mode 100644
index 0000000..fcb5829
--- /dev/null
+++ b/src/test/MergingTablesTest.java
@@ -0,0 +1,83 @@
+import org.junit.jupiter.api.Test;
+
+import java.io.*;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class MergingTablesTest {
+    @Test
+    void test() {
+        MergingTables.InputReader reader = new MergingTables.InputReader(System.in);
+        MergingTables.OutputWriter writer = new MergingTables.OutputWriter(System.out);
+        MergingTables mergingTables = new MergingTables(reader, writer);
+        mergingTables.tables = new MergingTables.Table[5];
+
+        MergingTables.Table t0 = new MergingTables.Table(1);
+        MergingTables.Table t1 = new MergingTables.Table(1);
+        MergingTables.Table t2 = new MergingTables.Table(1);
+        MergingTables.Table t3 = new MergingTables.Table(1);
+        MergingTables.Table t4 = new MergingTables.Table(1);
+
+        mergingTables.tables[0] = t0;
+        mergingTables.tables[1] = t1;
+        mergingTables.tables[2] = t2;
+        mergingTables.tables[3] = t3;
+        mergingTables.tables[4] = t4;
+        mergingTables.maximumNumberOfRows = 1;
+        mergingTables.rank = new int[]{0, 0, 0, 0, 0};
+        mergingTables.parent = new int[]{0, 1, 2, 3, 4};
+
+        mergingTables.merge(2, 4);
+        assertEquals(2, mergingTables.maximumNumberOfRows);
+
+        mergingTables.merge(1, 3);
+        assertEquals(2, mergingTables.maximumNumberOfRows);
+
+        mergingTables.merge(0, 3);
+        assertEquals(3, mergingTables.maximumNumberOfRows);
+
+        mergingTables.merge(4, 3);
+        assertEquals(5, mergingTables.maximumNumberOfRows);
+
+        mergingTables.merge(4, 2);
+        assertEquals(5, mergingTables.maximumNumberOfRows);
+    }
+
+    @Test
+    void test1() {
+        MergingTables.InputReader reader = new MergingTables.InputReader(System.in);
+        MergingTables.OutputWriter writer = new MergingTables.OutputWriter(System.out);
+        MergingTables mergingTables = new MergingTables(reader, writer);
+        mergingTables.tables = new MergingTables.Table[6];
+
+        MergingTables.Table t0 = new MergingTables.Table(10);
+        MergingTables.Table t1 = new MergingTables.Table(0);
+        MergingTables.Table t2 = new MergingTables.Table(5);
+        MergingTables.Table t3 = new MergingTables.Table(0);
+        MergingTables.Table t4 = new MergingTables.Table(3);
+        MergingTables.Table t5 = new MergingTables.Table(3);
+
+        mergingTables.tables[0] = t0;
+        mergingTables.tables[1] = t1;
+        mergingTables.tables[2] = t2;
+        mergingTables.tables[3] = t3;
+        mergingTables.tables[4] = t4;
+        mergingTables.tables[5] = t5;
+        mergingTables.maximumNumberOfRows = 10;
+        mergingTables.rank = new int[]{0, 0, 0, 0, 0, 0};
+        mergingTables.parent = new int[]{0, 1, 2, 3, 4, 5};
+
+        mergingTables.merge(5, 5);
+        assertEquals(10, mergingTables.maximumNumberOfRows);
+
+        mergingTables.merge(5, 4);
+        assertEquals(10, mergingTables.maximumNumberOfRows);
+
+        mergingTables.merge(4, 3);
+        assertEquals(10, mergingTables.maximumNumberOfRows);
+
+        mergingTables.merge(3, 2);
+        assertEquals(11, mergingTables.maximumNumberOfRows);
+    }
+
+}
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