//get length of a LinkedList
private static int getLength(ListNode head)
{
int l = 0;
while (head.next != null) {
l++;
head = head.next;
}
return l;
}
//up level public method
public static ListNode getIntersection(ListNode head1, ListNode head2)
{
int l1 = getLength (head1);
int l2 = getLength (head2);
if (l1 > l2) {
int d = l1 - l2;
return getIntersectionHelper (d, head1, head2);
} else {
int d = l2 - l1;
return getIntersectionHelper (d, head2, head1);
}
}
//get intersection using two Linkedlist and the length difference
private static ListNode getIntersectionHelper(int d, ListNode head1, ListNode head2)
{
for (int i = 0; i < d; i++) {
if (head1 == null)
return null;
head1 = head1.next;
}
while (head1 != null && head2 != null) {
if (head1 == head2)
return head1;
head1 = head1.next;
head2 = head2.next;
}
return null;
}
public static void Main (string[] args)
{
ListNode node1 = new ListNode (1);
ListNode node2 = new ListNode (2);
ListNode node3 = new ListNode (3);
ListNode node4 = new ListNode (4);
ListNode node5 = new ListNode (5);
ListNode node6 = new ListNode(8);
ListNode node7 = new ListNode(9);
ListNode node8 = new ListNode (10);
node1.next = node2;
node2.next = node3;
node3.next = node4;
node4.next = node5;
node6.next = node7;
node7.next = node8;
node8.next = node2;
ListNode intersection = Finder.getIntersection (node1, node6);
while (node1 != null) {
Console.Write (node1.val + "->");
node1 = node1.next;
}
Console.WriteLine ();
while (node6 != null) {
Console.Write (node6.val + "->");
node6 = node6.next;
}
Console.WriteLine ();
Console.WriteLine(intersection.val);
}
public ListNode(int x)
{
val = x;
next = null;
}
