Fix Circular linked list (#2598)

DataStructures/Lists/CircleLinkedList.java

@@ -15,12 +15,14 @@ public class CircleLinkedList<E> {
   private int size;
   // this will point to dummy node;
   private Node<E> head = null;
+  private Node<E> tail = null; // keeping a tail pointer to keep track of the end of list
 
   // constructer for class.. here we will make a dummy node for circly linked list implementation
   // with reduced error catching as our list will never be empty;
   public CircleLinkedList() {
     // creation of the dummy node
     head = new Node<E>(null, head);
+    tail = head;
     size = 0;
   }
 
@@ -37,10 +39,43 @@ public class CircleLinkedList<E> {
       throw new NullPointerException("Cannot add null element to the list");
     }
     // head.next points to the last element;
-    head.next = new Node<E>(value, head);
+    if (tail == null){
+      tail = new Node<E>(value, head);
+      head.next = tail;
+    }
+    else{
+      tail.next = new Node<E>(value, head);
+      tail = tail.next;
+    }
     size++;
   }
 
+  // utility function for teraversing the list
+  public String toString(){
+    Node p = head.next;
+    String s = "[ ";
+    while(p!=head){
+      s += p.value;
+      s += " , ";
+      p = p.next;
+    }
+    return s + " ]";
+  }
+
+  public static void main(String args[]){
+    CircleLinkedList cl = new CircleLinkedList<Integer>();
+    cl.append(12);
+    System.out.println(cl);
+    cl.append(23);
+    System.out.println(cl);
+    cl.append(34);
+    System.out.println(cl);
+    cl.append(56);
+    System.out.println(cl);
+    cl.remove(3);
+    System.out.println(cl);
+  }
+
   public E remove(int pos) {
     if (pos > size || pos < 0) {
       // catching errors
@@ -58,6 +93,9 @@ public class CircleLinkedList<E> {
     // the last element will be assigned to the head.
     before.next = before.next.next;
     // scrubbing
+    if(destroy == tail){
+      tail = before;
+    }
     destroy = null;
     size--;
     return saved;