static void Main(string[] args)
{
Program p = new Program();
ListNode head = new ListNode(1);
ListNode ptr = head;
for (int i = 2; i < 9; i++)
{
ptr.next = new ListNode(i);
ptr = ptr.next;
}
p.Print(ptr = head);
Console.WriteLine();
p.Print(p.OddEvenList(head));
Console.WriteLine();
Console.ReadKey();
}
public ListNode OddEvenList(ListNode head)
{
if (head == null) return head;
ListNode oddHead, oddPtr, evenHead, evenPtr, ptr;
oddHead = head;
oddPtr = head;
evenHead = new ListNode(-1);
evenHead.next = head.next;
evenPtr = evenHead;
// start from 2
ptr = head.next;
bool isOdd = false;
while (ptr != null)
{
if (isOdd)
{
oddPtr.next = ptr;
oddPtr = ptr;
isOdd = false;
}
else
{
evenPtr.next = ptr;
evenPtr = ptr;
isOdd = true;
}
ptr = ptr.next;
}
evenPtr.next = null;
oddPtr.next = evenHead.next;
return oddHead;
}
private void Print(ListNode node)
{
ListNode ptr = node;
while (ptr != null)
{
Console.Write(ptr.val);
ptr = ptr.next;
}
}
