剑指offer-反转链表

public ListNode ReverseList(ListNode head) {
ListNode pre=null,next;
while(head!=null)
{
next=head.next;
head.next=pre;
pre=head;
head=next;
}
return pre;
}

public ListNode ReverseList(ListNode head) {
ListNode phead=new ListNode(0);
ListNode pre,p;
p=pre=head;
while(pre!=null)
{
p=pre.next;
pre.next=phead.next;
phead.next=pre;
pre=p;
}
head=phead.next;

}