[LintCode]チェーンテーブルの最後からn番目のノードを削除

 1 /**
 2  * Definition of ListNode
 3  * class ListNode {
 4  * public:
 5  *     int val;
 6  *     ListNode *next;
 7  *     ListNode(int val) {
 8  *         this->val = val;
 9  *         this->next = NULL;
10  *     }
11  * }
12  */
13 class Solution {
14 public:
15     /**
16      * @param head: The first node of linked list.
17      * @param n: An integer.
18      * @return: The head of linked list.
19      */
20     ListNode *removeNthFromEnd(ListNode *head, int n) {
21         // write your code here
22         ListNode* pre = head;
23         ListNode* cur = head;
24         for (int i = 0; i < n; i++)
25             cur = cur -> next;
26         if (!cur) {
27             delete pre;
28             return pre -> next;
29         }
30         while (cur -> next) {
31             pre = pre -> next;
32             cur = cur -> next;
33         }
34         delete pre -> next;
35         pre -> next = pre -> next -> next;
36         return head;
37     }
38 };