static HeadTail ReverseR(LinkListNode head)
{
if (head == null)
{
return(null);
}
else
{
HeadTail headTail = ReverseR(head.next);
if (headTail == null)
{
LinkListNode tail = head.clone();
tail.next = null;
//LinkListNode returnHead = tail;
return(new HeadTail(tail, tail));
}
else
{
LinkListNode node = head.clone();
node.next = null;
headTail.Tail.next = node;
return(new HeadTail(headTail.Head, node));
}
}
}
public LinkListNode clone()
{
LinkListNode next2 = null;
if (next != null)
{
next2 = next.clone();
}
LinkListNode head2 = new LinkListNode(data, next2, null);
return(head2);
}
{//Palindrom: Implement a function to check if a linked list is a palindrom.
static void Main(string[] args)
{
//3210123
int[] a1 = new int[] { 3, 2, 1, 0, 1, 2, 3 };
LinkListNode n3210123 = BuildListWithArray(a1);
LinkListNode n3210123_clone1 = n3210123.clone();
LinkListNode n3210123_clone2 = n3210123.clone();
bool r1 = isPanlindrom(n3210123);
bool r1half = isPanlindromReverseHalf(n3210123_clone1);
bool r1r = isPanlindromR(n3210123_clone2);
Console.WriteLine("Results: {0}, {1}, {2} for Node {3}", r1, r1half, r1r, n3210123.printForward());
//32100123
int[] a2 = new int[] { 3, 2, 1, 0, 0, 1, 2, 3 };
LinkListNode n32100123 = BuildListWithArray(a2);
LinkListNode n32100123_clone1 = n32100123.clone();
LinkListNode n32100123_clone2 = n32100123.clone();
bool r2 = isPanlindrom(n32100123);
bool r2half = isPanlindromReverseHalf(n32100123_clone1);
bool r2r = isPanlindromR(n32100123_clone2);
Console.WriteLine("Results: {0}, {1}, {2} for Node {3}", r2, r2half, r2r, n32100123.printForward());
//4321908
int[] a3 = new int[] { 4, 3, 2, 1, 9, 0, 8 };
LinkListNode n4321908 = BuildListWithArray(a3);
LinkListNode n4321908_clone1 = n4321908.clone();
LinkListNode n4321908_clone2 = n4321908.clone();
bool r3 = isPanlindrom(n4321908);
bool r3half = isPanlindromReverseHalf(n4321908_clone1);
bool r3r = isPanlindromR(n4321908_clone2);
Console.WriteLine("Results: {0}, {1}, {2} for Node {3}", r3, r3half, r3r, n4321908.printForward());
}
//Method 1: reverse the whole list, check with the original one. O(n) time, O(n) space.
static bool isPanlindrom(LinkListNode head)
{
LinkListNode reverseNode = head.clone();
//reverseNode = Reverse(reverseNode);
reverseNode = ReverseRec(head);
while (head != null) {
if (head.data != reverseNode.data)
return false;
reverseNode = reverseNode.next;
head = head.next;
}
return true;
}
//Method 1: reverse the whole list, check with the original one. O(n) time, O(n) space.
static bool isPanlindrom(LinkListNode head)
{
LinkListNode reverseNode = head.clone();
//reverseNode = Reverse(reverseNode);
reverseNode = ReverseRec(head);
while (head != null)
{
if (head.data != reverseNode.data)
{
return(false);
}
reverseNode = reverseNode.next;
head = head.next;
}
return(true);
}
static HeadTail ReverseR(LinkListNode head)
{
if (head == null)
return null;
else {
HeadTail headTail = ReverseR(head.next);
if (headTail == null)
{
LinkListNode tail = head.clone();
tail.next = null;
//LinkListNode returnHead = tail;
return new HeadTail(tail, tail);
}
else {
LinkListNode node = head.clone();
node.next = null;
headTail.Tail.next = node;
return new HeadTail(headTail.Head, node);
}
}
}
