From c972499406015e0f0c73120858cecce48bc092de Mon Sep 17 00:00:00 2001
From: alxkm <alexanderklmn@gmail.com>
Date: Thu, 24 Jul 2025 16:46:43 +0200
Subject: [PATCH 1/2] testing: improve DisjointSetUnionTest

---
 .../DisjointSetUnionTest.java                 | 106 ++++++++++++++++++
 1 file changed, 106 insertions(+)

diff --git a/src/test/java/com/thealgorithms/datastructures/disjointsetunion/DisjointSetUnionTest.java b/src/test/java/com/thealgorithms/datastructures/disjointsetunion/DisjointSetUnionTest.java
index 14dceb53c40d..39c45a2b85c7 100644
--- a/src/test/java/com/thealgorithms/datastructures/disjointsetunion/DisjointSetUnionTest.java
+++ b/src/test/java/com/thealgorithms/datastructures/disjointsetunion/DisjointSetUnionTest.java
@@ -122,4 +122,110 @@ public void testPathCompression() {
         assertEquals(root, node1);
         assertEquals(node1, node3.parent);
     }
+
+    @Test
+    public void testUnionByRankSmallerToLarger() {
+        DisjointSetUnion<Integer> dsu = new DisjointSetUnion<>();
+        Node<Integer> node1 = dsu.makeSet(1);
+        Node<Integer> node2 = dsu.makeSet(2);
+        Node<Integer> node3 = dsu.makeSet(3);
+        Node<Integer> node4 = dsu.makeSet(4);
+
+        // Create tree with node1 as root and rank 1
+        dsu.unionSets(node1, node2);
+        assertEquals(1, node1.rank);
+        assertEquals(0, node2.rank);
+
+        // Union single node (rank 0) with tree (rank 1)
+        // Smaller rank tree should attach to larger rank tree
+        dsu.unionSets(node3, node1);
+        assertEquals(node1, dsu.findSet(node3));
+        assertEquals(1, node1.rank); // Rank should not increase
+    }
+
+    @Test
+    public void testUnionByRankEqualRanks() {
+        DisjointSetUnion<Integer> dsu = new DisjointSetUnion<>();
+        Node<Integer> node1 = dsu.makeSet(1);
+        Node<Integer> node2 = dsu.makeSet(2);
+        Node<Integer> node3 = dsu.makeSet(3);
+        Node<Integer> node4 = dsu.makeSet(4);
+
+        // Create two trees of equal rank (1)
+        dsu.unionSets(node1, node2);
+        dsu.unionSets(node3, node4);
+        assertEquals(1, node1.rank);
+        assertEquals(1, node3.rank);
+
+        // Union two trees of equal rank
+        dsu.unionSets(node1, node3);
+        Node<Integer> root = dsu.findSet(node1);
+        assertEquals(2, root.rank); // Rank should increase by 1
+    }
+
+    @Test
+    public void testLargeChainPathCompression() {
+        DisjointSetUnion<Integer> dsu = new DisjointSetUnion<>();
+        Node<Integer> node1 = dsu.makeSet(1);
+        Node<Integer> node2 = dsu.makeSet(2);
+        Node<Integer> node3 = dsu.makeSet(3);
+        Node<Integer> node4 = dsu.makeSet(4);
+        Node<Integer> node5 = dsu.makeSet(5);
+
+        // Create a long chain: 1 -> 2 -> 3 -> 4 -> 5
+        dsu.unionSets(node1, node2);
+        dsu.unionSets(node2, node3);
+        dsu.unionSets(node3, node4);
+        dsu.unionSets(node4, node5);
+
+        // Find from the deepest node
+        Node<Integer> root = dsu.findSet(node5);
+
+        // Path compression should make all nodes point directly to root
+        assertEquals(root, node5.parent);
+        assertEquals(root, node4.parent);
+        assertEquals(root, node3.parent);
+        assertEquals(root, node2.parent);
+        assertEquals(root, node1.parent);
+    }
+
+    @Test
+    public void testMultipleDisjointSets() {
+        DisjointSetUnion<Integer> dsu = new DisjointSetUnion<>();
+        Node<Integer> node1 = dsu.makeSet(1);
+        Node<Integer> node2 = dsu.makeSet(2);
+        Node<Integer> node3 = dsu.makeSet(3);
+        Node<Integer> node4 = dsu.makeSet(4);
+        Node<Integer> node5 = dsu.makeSet(5);
+        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() {
+        DisjointSetUnion<String> dsu = new DisjointSetUnion<>();
+        Node<String> emptyNode = dsu.makeSet("");
+        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));
+    }
 }

From 56a42aa6bc86972bd02b7b8144d6447a90d6f18b Mon Sep 17 00:00:00 2001
From: alxkm <alexanderklmn@gmail.com>
Date: Thu, 24 Jul 2025 16:57:57 +0200
Subject: [PATCH 2/2] testing: redundant variable for DisjointSetUnionTest

---
 .../datastructures/disjointsetunion/DisjointSetUnionTest.java    | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/test/java/com/thealgorithms/datastructures/disjointsetunion/DisjointSetUnionTest.java b/src/test/java/com/thealgorithms/datastructures/disjointsetunion/DisjointSetUnionTest.java
index 39c45a2b85c7..581bac6151dd 100644
--- a/src/test/java/com/thealgorithms/datastructures/disjointsetunion/DisjointSetUnionTest.java
+++ b/src/test/java/com/thealgorithms/datastructures/disjointsetunion/DisjointSetUnionTest.java
@@ -129,7 +129,6 @@ public void testUnionByRankSmallerToLarger() {
         Node<Integer> node1 = dsu.makeSet(1);
         Node<Integer> node2 = dsu.makeSet(2);
         Node<Integer> node3 = dsu.makeSet(3);
-        Node<Integer> node4 = dsu.makeSet(4);
 
         // Create tree with node1 as root and rank 1
         dsu.unionSets(node1, node2);

<!DOCTYPE html PUBLIC '-//W3C//DTD XHTML 1.0 Transitional//EN' 'http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd'>
<html xmlns='http://www.w3.org/1999/xhtml'>
<head>
<title>pFad - Phonifier reborn</title>
<meta http-equiv='Content-Type' content='text/html; charset=utf-8' />
</head>
<body>
<h1>Pfad - The Proxy pFad of &#169; 2024 Garber Painting. All rights reserved.</h1>


<!-- Disclaimer -->
<p>Note: This service is not intended for secure transactions such as banking, social media, email, or purchasing. Use at your own risk. We assume no liability whatsoever for broken pages.</p>
<br>
<p>Alternative Proxies:</p><p><a href="http://rainy.clevelandohioweatherforecast.com/php-proxy/index.php?q=https://patch-diff.githubusercontent.com/raw/TheAlgorithms/Java/pull/6440.patch" target="_blank">Alternative Proxy</a></p><p><a href="http://rainy.clevelandohioweatherforecast.com/pFad/index.php?u=https://patch-diff.githubusercontent.com/raw/TheAlgorithms/Java/pull/6440.patch" target="_blank">pFad Proxy</a></p><p><a href="http://rainy.clevelandohioweatherforecast.com/pFad/v3index.php?u=https://patch-diff.githubusercontent.com/raw/TheAlgorithms/Java/pull/6440.patch" target="_blank">pFad v3 Proxy</a></p><p><a href="http://rainy.clevelandohioweatherforecast.com/pFad/v4index.php?u=https://patch-diff.githubusercontent.com/raw/TheAlgorithms/Java/pull/6440.patch" target="_blank">pFad v4 Proxy</a></p></body>
</html>