static ListNode Revese(ListNode head, int k)
{
ListNode preNode = head;
ListNode n1 = head.next;
if (n1 == null)
{
return(null);
}
ListNode kNode = preNode;
for (int i = 0; i < k; i++)
{
if (kNode == null)
{
return(null);
}
kNode = kNode.next;
}
if (kNode == null)
{
return(null);
}
ListNode kPlus = kNode.next;
ListNode cur = n1;
while (cur != kPlus)
{
ListNode temp = cur.next;
cur.next = preNode;
preNode = cur;
cur = temp;
}
head.next = preNode;
n1.next = kPlus;
return(n1);
}