public CtciLinkedListNode <T> FindBeginning(CtciLinkedListNode <T> head)
{
if (head == null)
{
throw new Exception("Incorrect Data");
}
CtciLinkedListNode <T> slow = head;
CtciLinkedListNode <T> fast = head;
do
{
if (fast.Next == null || fast.Next.Next == null)
{
return(null);
}
slow = slow.Next;
fast = fast.Next.Next;
} while (slow != fast);
slow = head;
while (slow != fast)
{
slow = slow.Next;
fast = fast.Next;
}
return(slow);
}
public Q07_Result <T> FindLengthAndLastNode(CtciLinkedListNode <T> listNode)
{
int length = 1;
while (listNode.Next != null)
{
listNode = listNode.Next;
length++;
}
return(new Q07_Result <T>(length, listNode));
}
public CtciLinkedListNode <T> FindIntersection(CtciLinkedListNode <T> listNode1, CtciLinkedListNode <T> listNode2)
{
if (listNode1 == null || listNode2 == null)
{
throw new Exception("Incorrect Data");
}
Q07_Result <T> result1 = FindLengthAndLastNode(listNode1);
Q07_Result <T> result2 = FindLengthAndLastNode(listNode2);
if (result1.lastNode != result2.lastNode)
{
return(null);
}
CtciLinkedListNode <T> longer;
CtciLinkedListNode <T> shorter;
if (result1.length >= result2.length)
{
longer = listNode1;
shorter = listNode2;
}
else
{
longer = listNode2;
shorter = listNode1;
}
int diff = result1.length - result2.length;
for (int i = 0; i < diff; i++)
{
longer = longer.Next;
}
while (longer != null)
{
if (longer == shorter)
{
return(longer);
}
longer = longer.Next;
shorter = shorter.Next;
}
return(null);
}
public void FindIntersection()
{
CtciLinkedListNode <int> listHead1 = new CtciLinkedListNode <int>(1);
CtciLinkedListNode <int> listHead2 = new CtciLinkedListNode <int>(1);
CtciLinkedListNode <int> node1 = new CtciLinkedListNode <int>(1);
CtciLinkedListNode <int> node2 = new CtciLinkedListNode <int>(1);
CtciLinkedListNode <int> node3 = new CtciLinkedListNode <int>(1);
CtciLinkedListNode <int> node4 = new CtciLinkedListNode <int>(1);
CtciLinkedListNode <int> node5 = new CtciLinkedListNode <int>(1);
CtciLinkedListNode <int> node6 = new CtciLinkedListNode <int>(1);
CtciLinkedListNode <int> node7 = new CtciLinkedListNode <int>(1);
CtciLinkedListNode <int> node8 = new CtciLinkedListNode <int>(1);
CtciLinkedListNode <int> node9 = new CtciLinkedListNode <int>(1);
CtciLinkedListNode <int> node10 = new CtciLinkedListNode <int>(1);
CtciLinkedListNode <int> node11 = new CtciLinkedListNode <int>(1);
CtciLinkedListNode <int> node12 = new CtciLinkedListNode <int>(1);
listHead1.Next = node1;
node1.Next = node2;
node2.Next = node3;
node3.Next = node4;
node4.Next = node5;
node5.Next = node6;
node6.Next = node7;
node7.Next = node8;
node8.Next = node9;
node9.Next = node10;
listHead2.Next = node11;
node11.Next = node12;
Assert.Equal(null, intersection.FindIntersection(listHead1, listHead2));
node12.Next = node6;
Assert.Equal(node6, intersection.FindIntersection(listHead1, listHead2));
}
public void FindBeginning()
{
CtciLinkedListNode <int> node1 = new CtciLinkedListNode <int>(1);
CtciLinkedListNode <int> node2 = new CtciLinkedListNode <int>(2);
CtciLinkedListNode <int> node3 = new CtciLinkedListNode <int>(3);
CtciLinkedListNode <int> node4 = new CtciLinkedListNode <int>(4);
CtciLinkedListNode <int> node5 = new CtciLinkedListNode <int>(5);
CtciLinkedListNode <int> node6 = new CtciLinkedListNode <int>(6);
CtciLinkedListNode <int> node7 = new CtciLinkedListNode <int>(7);
CtciLinkedListNode <int> node8 = new CtciLinkedListNode <int>(8);
CtciLinkedListNode <int> node9 = new CtciLinkedListNode <int>(9);
CtciLinkedListNode <int> node10 = new CtciLinkedListNode <int>(10);
CtciLinkedListNode <int> node11 = new CtciLinkedListNode <int>(11);
CtciLinkedListNode <int> node12 = new CtciLinkedListNode <int>(12);
node1.Next = node2;
node2.Next = node3;
node3.Next = node4;
node4.Next = node5;
node5.Next = node6;
node6.Next = node7;
node7.Next = node8;
node8.Next = node9;
node9.Next = node10;
node10.Next = node11;
node11.Next = node12;
node12.Next = node5;
Assert.Equal(node5, loopDetection.FindBeginning(node1));
node12.Next = node7;
Assert.Equal(node7, loopDetection.FindBeginning(node1));
node12.Next = null;
Assert.Null(loopDetection.FindBeginning(node1));
}
public Q07_Result(int length, CtciLinkedListNode <T> lastNode)
{
this.length = length;
this.lastNode = lastNode;
}
