public ListNode RemoveNthFromEnd(ListNode head, int n)
{
var p = new ListNode(0);
var tmp = new ListNode(0);
p.next = head;
tmp.next = head;
while (--n >= 0)
{
p = p.next;
}
if (p.next == null)
{
head = head.next;
}
else
{
while (p.next != null)
{
p = p.next;
tmp = tmp.next;
}
tmp = tmp.next;
}
return head;
}
public ListNode MergeTwoLists(ListNode l1, ListNode l2)
{
if (l1 == null) return l2;
if (l2 == null) return l1;
ListNode p1 = new ListNode(0);
ListNode p2 = new ListNode(0);
ListNode prev = new ListNode(0);
p1.next = l1;
p2.next = l2;
while (p2.next != null && p1.next.val >= p2.next.val)
{
prev.next = p2.next;
p2.next = p2.next.next;
prev.next.next = p1.next;
l1 = prev.next;
}
while (p1.next != null && p2.next != null)
{
if (p1.next.val < p2.next.val)
{
prev.next = p1.next;
p1.next = p1.next.next;
}
else
{
prev.next.next = p2.next;
p2.next = p2.next.next;
prev.next.next.next = p1.next;
}
}
if (p1.next == null)
{
prev.next = p2.next;
}
return l1;
}