[LintCode] 删除链表中倒数第n个节点

 /**
  * Definition of ListNode
  * class ListNode {
  * public:
  *     int val;
  *     ListNode *next;
  *     ListNode(int val) {
  *         this->val = val;
  *         this->next = NULL;
  *     }
  * }
  */
 class Solution {
 public:
     /**
      * @param head: The first node of linked list.
      * @param n: An integer.
      * @return: The head of linked list.
      */
     ListNode *removeNthFromEnd(ListNode *head, int n) {
         // write your code here
         ListNode* pre = head;
         ListNode* cur = head;
         for (int i = ; i < n; i++)
             cur = cur -> next;
         if (!cur) {
             delete pre;
             return pre -> next;
         }
         while (cur -> next) {
             pre = pre -> next;
             cur = cur -> next;
         }
         delete pre -> next;
         pre -> next = pre -> next -> next;
         return head;
     }
 };