public void appendToTail(int d)
{
Node end = new Node(d);
Node n = this;
while (n.next != null)
{
n = n.next;
}
n.next = end;
}
public static void print_node(Node node)
{
Console.WriteLine("node level 1: " + node.data);
Node head = node;
int levels = 2;
while (head.next != null)
{
head = head.next;
Console.WriteLine("node level " + levels + ": " + head.data);
levels++;
if (levels > 15)
break;
}
}
public static Node find_circular_reference(Node head)
{
Hashtable values = new Hashtable();
Node runner = head;
while (runner.next != null)
{
runner = runner.next;
if (values.ContainsKey(runner.data))
{
return runner;
}
else
values.Add(runner.data, true);
}
return null;
}
static void Main(string[] args)
{
//
// Question 2.6
//
// Given a circular linked list, implement an algorithm which returns
// the node at the beginning of the loop.
// DEFINITION
// Circular linked list: A (corrupt linked list in which a node's next pointer
// points to an earlier node, so as to make a loop in the linked list.
// EXAMPLE
// Input: A -> B -> C -> D -> E -> C [the same C as earlier]
// Output: C
//
Random rand = new Random();
Node valid_list = new Node(400);
for (int x = 0; x <= 4; x++)
{
valid_list.appendToTail(rand.Next(0, 100));
}
Console.WriteLine("Valid list: ");
print_node(valid_list);
Node bork = find_circular_reference(valid_list);
if (bork != null) { Console.WriteLine("Found circular reference: " + bork.data); }
Node corrupt_list = new Node(500);
for (int x = 0; x <= 4; x++)
{
corrupt_list.appendToTail(rand.Next(0, 50));
}
Node circular = corrupt_list.next.next;
Node runner = corrupt_list;
while (runner.next != null)
{
runner = runner.next;
}
runner.next = circular;
Console.WriteLine("Corrupt list: ");
print_node(corrupt_list);
bork = find_circular_reference(corrupt_list);
if (bork != null) { Console.WriteLine("Found circular reference: " + bork.data); }
Console.ReadLine();
}
