delete lesser nodes: done (recursive version)

Author: Ram swaroop

src/me/ramswaroop/common/CircularSingleLinkedList.java

@@ -181,7 +181,11 @@ public int size() {
 
     @Override
     public void printList() {
-        SingleLinkedNode<E> curr = head;
+        printList(head);
+    }
+
+    public void printList(SingleLinkedNode<E> node) {
+        SingleLinkedNode<E> curr = node;
         out.print("[");
         if (curr == null) {
             out.println("]");

src/me/ramswaroop/common/DoubleLinkedList.java

@@ -175,7 +175,11 @@ public int size() {
 
     @Override
     public void printList() {
-        DoubleLinkedNode<E> curr = head;
+        printList(head);
+    }
+
+    public void printList(DoubleLinkedNode<E> node) {
+        DoubleLinkedNode<E> curr = node;
         out.print("[");
         if (curr == null) {
             out.println("]");

src/me/ramswaroop/common/SingleLinkedList.java

@@ -161,7 +161,11 @@ public int size() {
 
     @Override
     public void printList() {
-        SingleLinkedNode<E> curr = head;
+        printList(head);
+    }
+
+    public void printList(SingleLinkedNode<E> node) {
+        SingleLinkedNode<E> curr = node;
         out.print("[");
         if (curr == null) {
             out.println("]");

src/me/ramswaroop/linkedlists/DeleteLesserNodes.java

@@ -15,15 +15,15 @@ public class DeleteLesserNodes {
     /**
      * Delete a node from {@param list} if there are any nodes
      * with values greater than node on the right hand side of the list.
-     *
+     * <p/>
      * Example:
-     *
+     * <p/>
      * Input:   12->15->10->11->5->6->2->3->NULL
      * Output:  15->11->6->3->NULL
-     *
+     * <p/>
      * Input:   10->20->30->40->50->60->NULL
      * Output:  60->NULL
-     *
+     * <p/>
      * Input:   60->50->40->30->20->10->NULL
      * Output:  60->50->40->30->20->10->NULL
      *
@@ -55,6 +55,27 @@ public static <E extends Comparable<E>> void deleteLesserNodes(SingleLinkedList<
         ReverseSingleLinkedList.reverseList(list);
     }
 
+
+    /**
+     * Recursive version of {@link #deleteLesserNodes(me.ramswaroop.common.SingleLinkedList)}.
+     *
+     * @param node
+     * @param <E>
+     * @return
+     */
+    public static <E extends Comparable<E>> SingleLinkedNode<E> deleteLesserNodes(SingleLinkedNode<E> node) {
+        if (node == null) return null;
+
+        SingleLinkedNode<E> next = deleteLesserNodes(node.next);
+        node.next = next;
+
+        if (next != null && node.item.compareTo(next.item) < 0) {
+            return next;
+        } else {
+            return node;
+        }
+    }
+
     public static void main(String a[]) {
         SingleLinkedList<Integer> linkedList = new SingleLinkedList<>();
         linkedList.add(00);
@@ -67,5 +88,14 @@ public static void main(String a[]) {
         linkedList.printList();
         deleteLesserNodes(linkedList);
         linkedList.printList();
+        // for recursive version
+        linkedList.add(00);
+        linkedList.add(11);
+        linkedList.add(22);
+        linkedList.add(33);
+        linkedList.add(44);
+        linkedList.add(55);
+        linkedList.printList();
+        linkedList.printList(deleteLesserNodes(linkedList.head));
     }
 }