Merge branch 'master' into add-library-sort

Author: Rosander0

.github/workflows/build.yml

@@ -10,7 +10,7 @@ jobs:
     steps:
       - uses: actions/checkout@v7
       - name: Set up JDK
-        uses: actions/setup-java@v5.4.0
+        uses: actions/setup-java@v5.5.0
         with:
           java-version: 21
           distribution: 'temurin'

.github/workflows/codeql.yml

@@ -24,21 +24,21 @@ jobs:
         uses: actions/checkout@v7
 
       - name: Set up JDK
-        uses: actions/setup-java@v5.4.0
+        uses: actions/setup-java@v5.5.0
         with:
           java-version: 21
           distribution: 'temurin'
 
       - name: Initialize CodeQL
-        uses: github/codeql-action/init@v4.36.2
+        uses: github/codeql-action/init@v4.36.3
         with:
           languages: 'java-kotlin'
 
       - name: Build
         run: mvn --batch-mode --update-snapshots verify
 
       - name: Perform CodeQL Analysis
-        uses: github/codeql-action/analyze@v4.36.2
+        uses: github/codeql-action/analyze@v4.36.3
         with:
           category: "/language:java-kotlin"
 
@@ -55,12 +55,12 @@ jobs:
         uses: actions/checkout@v7
 
       - name: Initialize CodeQL
-        uses: github/codeql-action/init@v4.36.2
+        uses: github/codeql-action/init@v4.36.3
         with:
           languages: 'actions'
 
       - name: Perform CodeQL Analysis
-        uses: github/codeql-action/analyze@v4.36.2
+        uses: github/codeql-action/analyze@v4.36.3
         with:
           category: "/language:actions"
 ...

.github/workflows/infer.yml

@@ -18,7 +18,7 @@ jobs:
       - uses: actions/checkout@v7
 
       - name: Set up JDK
-        uses: actions/setup-java@v5.4.0
+        uses: actions/setup-java@v5.5.0
         with:
           java-version: 21
           distribution: 'temurin'

.github/workflows/stale.yml

@@ -11,7 +11,7 @@ jobs:
       pull-requests: write
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/stale@v10
+      - uses: actions/stale@v10.3.0
         with:
           stale-issue-message: 'This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contribution!'
           close-issue-message: 'Please reopen this issue once you have made the required changes. If you need help, feel free to ask in our [Discord](https://the-algorithms.com/discord) server or ping one of the maintainers here. Thank you for your contribution!'

src/main/java/com/thealgorithms/graph/AccountMerge.java

@@ -10,13 +10,25 @@
 /**
  * Merges account records using Disjoint Set Union (Union-Find) on shared emails.
  *
- * <p>Input format: each account is a list where the first element is the user name and the
- * remaining elements are emails.
+ * <p>Each account is expected to be a list where the first element is the user name and the
+ * remaining elements are email addresses. Accounts that share at least one email are merged into a
+ * single record.
  */
 public final class AccountMerge {
     private AccountMerge() {
+        // Utility class; do not instantiate.
     }
 
+    /**
+     * Merges accounts that share one or more email addresses.
+     *
+     * <p>The returned list is sorted by account owner name, then by the first email address when
+     * multiple merged groups have the same owner name. Within each merged account, emails are
+     * returned in lexicographic order.
+     *
+     * @param accounts a list of accounts where each entry contains a user name followed by emails
+     * @return merged accounts, or an empty list when {@code accounts} is null or empty
+     */
     public static List<List<String>> mergeAccounts(List<List<String>> accounts) {
         if (accounts == null || accounts.isEmpty()) {
             return List.of();
@@ -73,6 +85,9 @@ public static List<List<String>> mergeAccounts(List<List<String>> accounts) {
         return merged;
     }
 
+    /**
+     * Lightweight union-find structure with path compression and union by rank.
+     */
     private static final class UnionFind {
         private final int[] parent;
         private final int[] rank;