public void setPrevious(LinkListNode p)
{
prev = p;
if (p != null && p.next != this)
{
p.setNext(this);
}
}
public LinkListNode clone()
{
LinkListNode next2 = null;
if (next != null)
{
next2 = next.clone();
}
LinkListNode head2 = new LinkListNode(data, next2, null);
return head2;
}
public LinkListNode clone()
{
LinkListNode next2 = null;
if (next != null)
{
next2 = next.clone();
}
LinkListNode head2 = new LinkListNode(data, next2, null);
return(head2);
}
public void setNext(LinkListNode n)
{
next = n;
if (this == last)
{
last = n;
}
if (n != null && n.prev != this)
{
n.setPrevious(this);
}
}
public void setNext(LinkListNode n)
{
next = n;
if (this == last)
{
last = n;
}
if (n != null && n.prev != this)
{
n.setPrevious(this);
}
}
static LinkListNode isLoop(LinkListNode head)
{
LinkListNode slow = head;
LinkListNode fast = head;
while (fast != null && fast.next != null) {
slow = slow.next;
fast = fast.next.next;
if (slow == fast) { //loop
slow = head;
while (slow != fast){
slow = slow.next;
fast = fast.next;
}
return slow;
}
} // if hit end of outer while loop, means not loop
return null;
}
static void Main(string[] args)
{
//Loop Detection: Given a circular linked list, implement an algrithm that returns the node at the beginning of the loop.
LinkListNode n1 = new LinkListNode(1);
n1.next = new LinkListNode(2);
n1.next.next = new LinkListNode(3);
LinkListNode collision = new LinkListNode(4);
n1.next.next = collision;
collision.next = new LinkListNode(5);
collision.next.next = new LinkListNode(6);
collision.next.next.next = new LinkListNode(7);
collision.next.next.next.next = new LinkListNode(8);
collision.next.next.next.next.next = new LinkListNode(9);
collision.next.next.next.next.next.next = collision;
if (isLoop(n1) != null)
Console.WriteLine(isLoop(n1).data);
else
Console.WriteLine("Not a loop");
}
public LinkListNode(int d, LinkListNode n, LinkListNode p)
{
data = d;
setNext(n);
setPrevious(p);
}
public LinkListNode(int d, LinkListNode n, LinkListNode p)
{
data = d;
setNext(n);
setPrevious(p);
}