refactor: introduce SinglyLinkedListNode (#6210)

Author: vil02

src/main/java/com/thealgorithms/datastructures/lists/CountSinglyLinkedListRecursion.java

@@ -12,7 +12,7 @@ public class CountSinglyLinkedListRecursion extends SinglyLinkedList {
      * @param head the head node of the list segment being counted.
      * @return the count of nodes from the given head node onward.
      */
-    private int countRecursion(Node head) {
+    private int countRecursion(SinglyLinkedListNode head) {
         return head == null ? 0 : 1 + countRecursion(head.next);
     }
 

src/main/java/com/thealgorithms/datastructures/lists/MergeSortedSinglyLinkedList.java

@@ -42,12 +42,12 @@ public static SinglyLinkedList merge(SinglyLinkedList listA, SinglyLinkedList li
             throw new NullPointerException("Input lists must not be null.");
         }
 
-        Node headA = listA.getHead();
-        Node headB = listB.getHead();
+        SinglyLinkedListNode headA = listA.getHead();
+        SinglyLinkedListNode headB = listB.getHead();
         int size = listA.size() + listB.size();
 
-        Node head = new Node();
-        Node tail = head;
+        SinglyLinkedListNode head = new SinglyLinkedListNode();
+        SinglyLinkedListNode tail = head;
         while (headA != null && headB != null) {
             if (headA.value <= headB.value) {
                 tail.next = headA;

src/main/java/com/thealgorithms/datastructures/lists/QuickSortLinkedList.java

@@ -105,7 +105,7 @@
 public class QuickSortLinkedList {
 
     private final SinglyLinkedList list; // The linked list to be sorted
-    private Node head; // Head of the list
+    private SinglyLinkedListNode head; // Head of the list
 
     /**
      * Constructor that initializes the QuickSortLinkedList with a given linked list.
@@ -136,19 +136,19 @@ public void sortList() {
      * @param head The head node of the list to sort
      * @return The head node of the sorted linked list
      */
-    private Node sortList(Node head) {
+    private SinglyLinkedListNode sortList(SinglyLinkedListNode head) {
         if (head == null || head.next == null) {
             return head;
         }
 
-        Node pivot = head;
+        SinglyLinkedListNode pivot = head;
         head = head.next;
         pivot.next = null;
 
-        Node lessHead = new Node();
-        Node lessTail = lessHead;
-        Node greaterHead = new Node();
-        Node greaterTail = greaterHead;
+        SinglyLinkedListNode lessHead = new SinglyLinkedListNode();
+        SinglyLinkedListNode lessTail = lessHead;
+        SinglyLinkedListNode greaterHead = new SinglyLinkedListNode();
+        SinglyLinkedListNode greaterTail = greaterHead;
 
         while (head != null) {
             if (head.value < pivot.value) {
@@ -164,14 +164,14 @@ private Node sortList(Node head) {
         lessTail.next = null;
         greaterTail.next = null;
 
-        Node sortedLess = sortList(lessHead.next);
-        Node sortedGreater = sortList(greaterHead.next);
+        SinglyLinkedListNode sortedLess = sortList(lessHead.next);
+        SinglyLinkedListNode sortedGreater = sortList(greaterHead.next);
 
         if (sortedLess == null) {
             pivot.next = sortedGreater;
             return pivot;
         } else {
-            Node current = sortedLess;
+            SinglyLinkedListNode current = sortedLess;
             while (current.next != null) {
                 current = current.next;
             }

src/main/java/com/thealgorithms/datastructures/lists/ReverseKGroup.java

@@ -14,10 +14,10 @@
  * </p>
  * <p>
  * The implementation contains:
- * - {@code length(Node head)}: A method to calculate the length of the linked list.
- * - {@code reverse(Node head, int count, int k)}: A helper method that reverses the nodes
+ * - {@code length(SinglyLinkedListNode head)}: A method to calculate the length of the linked list.
+ * - {@code reverse(SinglyLinkedListNode head, int count, int k)}: A helper method that reverses the nodes
  *   in the linked list in groups of k.
- * - {@code reverseKGroup(Node head, int k)}: The main method that initiates the reversal
+ * - {@code reverseKGroup(SinglyLinkedListNode head, int k)}: The main method that initiates the reversal
  *   process by calling the reverse method.
  * </p>
  * <p>
@@ -38,8 +38,8 @@ public class ReverseKGroup {
      * @param head The head node of the linked list.
      * @return The total number of nodes in the linked list.
      */
-    public int length(Node head) {
-        Node curr = head;
+    public int length(SinglyLinkedListNode head) {
+        SinglyLinkedListNode curr = head;
         int count = 0;
         while (curr != null) {
             curr = curr.next;
@@ -56,14 +56,14 @@ public int length(Node head) {
      * @param k The size of the group to reverse.
      * @return The new head of the reversed linked list segment.
      */
-    public Node reverse(Node head, int count, int k) {
+    public SinglyLinkedListNode reverse(SinglyLinkedListNode head, int count, int k) {
         if (count < k) {
             return head;
         }
-        Node prev = null;
+        SinglyLinkedListNode prev = null;
         int count1 = 0;
-        Node curr = head;
-        Node next = null;
+        SinglyLinkedListNode curr = head;
+        SinglyLinkedListNode next = null;
         while (curr != null && count1 < k) {
             next = curr.next;
             curr.next = prev;
@@ -85,7 +85,7 @@ public Node reverse(Node head, int count, int k) {
      * @param k The size of the group to reverse.
      * @return The head of the modified linked list after reversal.
      */
-    public Node reverseKGroup(Node head, int k) {
+    public SinglyLinkedListNode reverseKGroup(SinglyLinkedListNode head, int k) {
         int count = length(head);
         return reverse(head, count, k);
     }

src/main/java/com/thealgorithms/datastructures/lists/RotateSinglyLinkedLists.java

@@ -38,12 +38,12 @@ public class RotateSinglyLinkedLists {
      * @param k The number of positions to rotate the list to the right.
      * @return The head of the rotated linked list.
      */
-    public Node rotateRight(Node head, int k) {
+    public SinglyLinkedListNode rotateRight(SinglyLinkedListNode head, int k) {
         if (head == null || head.next == null || k == 0) {
             return head;
         }
 
-        Node curr = head;
+        SinglyLinkedListNode curr = head;
         int len = 1;
         while (curr.next != null) {
             curr = curr.next;

src/main/java/com/thealgorithms/datastructures/lists/SearchSinglyLinkedListRecursion.java

@@ -30,7 +30,7 @@ public class SearchSinglyLinkedListRecursion extends SinglyLinkedList {
      * @param key the integer value to be searched for.
      * @return {@code true} if the value `key` is present in the list; otherwise, {@code false}.
      */
-    private boolean searchRecursion(Node node, int key) {
+    private boolean searchRecursion(SinglyLinkedListNode node, int key) {
         return (node != null && (node.value == key || searchRecursion(node.next, key)));
     }