单链表就地反转

 1 // 1.就地反转法  2 public ListNode reverseList1(ListNode head) {  3 if (head == null)  4 return head;  5 ListNode dummy = new ListNode(-1);  6 dummy.next = head;  7 ListNode prev = dummy.next;  8 ListNode pCur = prev.next;  9 while (pCur != null) { 10 prev.next = pCur.next; 11 pCur.next = dummy.next; 12 dummy.next = pCur; 13 pCur = prev.next; 14  } 15 return dummy.next; 16 }