LeetCode:Remove Nth Node From End of List

 1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     ListNode *next;
 6  *     ListNode(int x) : val(x), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11     ListNode* removeNthFromEnd(ListNode* head, int n) {
12     //题意是要删除从最后一个节点往前数的第n个节点 考虑到只有一个节点时没有办法删除 加一个dummy
13     
14     ListNode *dummy=new ListNode(-1);
15     dummy->next=head;
16     ListNode *pre=dummy;
17     ListNode *last=dummy;
18     
19     //找到last的初始位置
20     while(n--)
21     {
22         last=last->next;   
23     }
24     
25     while(last->next!=NULL)
26     {
27         pre=pre->next;
28         last=last->next;
29     }
30     //删除节点 
32     ListNode *object=pre->next;
33     pre->next=pre->next->next;
34     delete object;
35     
36     return dummy->next;
37     
38     }
39 };