Add tests for DisjointSetUnionBySize

Author: TIWARIPRIYANSH

src/test/java/com/thealgorithms/datastructures/disjointsetunion/DisjointSetUnionBySizeTest.java

@@ -0,0 +1,146 @@
+package com.thealgorithms.datastructures.disjointsetunion;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+import org.junit.jupiter.api.Test;
+
+public class DisjointSetUnionBySizeTest {
+
+    @Test
+    public void testMakeSet() {
+        DisjointSetUnionBySize<Integer> dsu = new DisjointSetUnionBySize<>();
+        DisjointSetUnionBySize.Node<Integer> node = dsu.makeSet(1);
+        assertNotNull(node);
+        assertEquals(node, node.parent);
+        assertEquals(1, node.size);
+    }
+
+    @Test
+    public void testUnionFindSet() {
+        DisjointSetUnionBySize<Integer> dsu = new DisjointSetUnionBySize<>();
+        DisjointSetUnionBySize.Node<Integer> node1 = dsu.makeSet(1);
+        DisjointSetUnionBySize.Node<Integer> node2 = dsu.makeSet(2);
+        DisjointSetUnionBySize.Node<Integer> node3 = dsu.makeSet(3);
+        DisjointSetUnionBySize.Node<Integer> node4 = dsu.makeSet(4);
+
+        dsu.unionSets(node1, node2);
+        dsu.unionSets(node3, node2);
+        dsu.unionSets(node3, node4);
+        dsu.unionSets(node1, node3);
+
+        DisjointSetUnionBySize.Node<Integer> root1 = dsu.findSet(node1);
+        DisjointSetUnionBySize.Node<Integer> root2 = dsu.findSet(node2);
+        DisjointSetUnionBySize.Node<Integer> root3 = dsu.findSet(node3);
+        DisjointSetUnionBySize.Node<Integer> root4 = dsu.findSet(node4);
+
+        assertEquals(root1, root2);
+        assertEquals(root1, root3);
+        assertEquals(root1, root4);
+        assertEquals(4, root1.size);
+    }
+
+    @Test
+    public void testFindSetOnSingleNode() {
+        DisjointSetUnionBySize<String> dsu = new DisjointSetUnionBySize<>();
+        DisjointSetUnionBySize.Node<String> node = dsu.makeSet("A");
+        assertEquals(node, dsu.findSet(node));
+    }
+
+    @Test
+    public void testUnionAlreadyConnectedNodes() {
+        DisjointSetUnionBySize<Integer> dsu = new DisjointSetUnionBySize<>();
+        DisjointSetUnionBySize.Node<Integer> node1 = dsu.makeSet(1);
+        DisjointSetUnionBySize.Node<Integer> node2 = dsu.makeSet(2);
+        DisjointSetUnionBySize.Node<Integer> node3 = dsu.makeSet(3);
+
+        dsu.unionSets(node1, node2);
+        dsu.unionSets(node2, node3);
+
+        // Union nodes that are already connected
+        dsu.unionSets(node1, node3);
+
+        // All should have the same root
+        DisjointSetUnionBySize.Node<Integer> root = dsu.findSet(node1);
+        assertEquals(root, dsu.findSet(node2));
+        assertEquals(root, dsu.findSet(node3));
+        assertEquals(3, root.size);
+    }
+
+    @Test
+    public void testMultipleMakeSets() {
+        DisjointSetUnionBySize<Integer> dsu = new DisjointSetUnionBySize<>();
+        DisjointSetUnionBySize.Node<Integer> node1 = dsu.makeSet(1);
+        DisjointSetUnionBySize.Node<Integer> node2 = dsu.makeSet(2);
+        DisjointSetUnionBySize.Node<Integer> node3 = dsu.makeSet(3);
+
+        assertNotEquals(node1, node2);
+        assertNotEquals(node2, node3);
+        assertNotEquals(node1, node3);
+
+        assertEquals(node1, node1.parent);
+        assertEquals(node2, node2.parent);
+        assertEquals(node3, node3.parent);
+        assertEquals(1, node1.size);
+        assertEquals(1, node2.size);
+        assertEquals(1, node3.size);
+    }
+
+    @Test
+    public void testPathCompression() {
+        DisjointSetUnionBySize<Integer> dsu = new DisjointSetUnionBySize<>();
+        DisjointSetUnionBySize.Node<Integer> node1 = dsu.makeSet(1);
+        DisjointSetUnionBySize.Node<Integer> node2 = dsu.makeSet(2);
+        DisjointSetUnionBySize.Node<Integer> node3 = dsu.makeSet(3);
+
+        dsu.unionSets(node1, node2);
+        dsu.unionSets(node2, node3);
+
+        // After findSet, path compression should update parent to root directly
+        DisjointSetUnionBySize.Node<Integer> root = dsu.findSet(node3);
+        assertEquals(root, node1);
+        assertEquals(node1, node3.parent);
+        assertEquals(3, root.size);
+    }
+
+    @Test
+    public void testMultipleDisjointSets() {
+        DisjointSetUnionBySize<Integer> dsu = new DisjointSetUnionBySize<>();
+        DisjointSetUnionBySize.Node<Integer> node1 = dsu.makeSet(1);
+        DisjointSetUnionBySize.Node<Integer> node2 = dsu.makeSet(2);
+        DisjointSetUnionBySize.Node<Integer> node3 = dsu.makeSet(3);
+        DisjointSetUnionBySize.Node<Integer> node4 = dsu.makeSet(4);
+        DisjointSetUnionBySize.Node<Integer> node5 = dsu.makeSet(5);
+        DisjointSetUnionBySize.Node<Integer> node6 = dsu.makeSet(6);
+
+        // Create two separate components
+        dsu.unionSets(node1, node2);
+        dsu.unionSets(node2, node3);
+
+        dsu.unionSets(node4, node5);
+        dsu.unionSets(node5, node6);
+
+        // Verify they are separate
+        assertEquals(dsu.findSet(node1), dsu.findSet(node2));
+        assertEquals(dsu.findSet(node2), dsu.findSet(node3));
+        assertEquals(dsu.findSet(node4), dsu.findSet(node5));
+        assertEquals(dsu.findSet(node5), dsu.findSet(node6));
+
+        assertNotEquals(dsu.findSet(node1), dsu.findSet(node4));
+        assertNotEquals(dsu.findSet(node3), dsu.findSet(node6));
+    }
+
+    @Test
+    public void testEmptyValues() {
+        DisjointSetUnionBySize<String> dsu = new DisjointSetUnionBySize<>();
+        DisjointSetUnionBySize.Node<String> emptyNode = dsu.makeSet("");
+        DisjointSetUnionBySize.Node<String> nullNode = dsu.makeSet(null);
+
+        assertEquals(emptyNode, dsu.findSet(emptyNode));
+        assertEquals(nullNode, dsu.findSet(nullNode));
+
+        dsu.unionSets(emptyNode, nullNode);
+        assertEquals(dsu.findSet(emptyNode), dsu.findSet(nullNode));
+    }
+}