1 /*
 2 struct ListNode {
 3     int val;
 4     struct ListNode *next;
 5     ListNode(int x) :
 6             val(x), next(NULL) {
 7     }
 8 };*/
 9 class Solution {
10 public:
11     ListNode* FindKthToTail(ListNode* pListHead, unsigned int k) {
12         ListNode *newphead = pListHead;
13         int total = 0;
14         while(newphead != NULL){
15             total++;
16             newphead = newphead->next;
17         }
18         newphead = pListHead;
19         int flag = total-k+1;
20         total = 0;
21         ListNode *result;
22         while(newphead != NULL){
23             total++;
24             if(total == flag){
25                 result = newphead;
26                 break;
27             }
28             newphead = newphead->next;
29         }
30         return result;
31     }
32 };

 1 /*
 2 struct ListNode {
 3     int val;
 4     struct ListNode *next;
 5     ListNode(int x) :
 6             val(x), next(NULL) {
 7     }
 8 };*/
 9 class Solution {
10 public:
11     ListNode* FindKthToTail(ListNode* pListHead, unsigned int k) {
12         if(pListHead == NULL )
13             return pListHead;
14         ListNode *p1 = pListHead;
15         ListNode *p2 = pListHead;
16         int step = 1;
17         while(step <= k){
18             if(p1->next != NULL)
19                 p1 = p1->next;
20             else{
21                 if(step == k)
22                     return p2;
23                 else
24                     return NULL;
25             }
26             step += 1;
27         }
28         while(p1 != NULL){
29             p1 = p1->next;
30             p2 = p2->next;
31         }
32         return p2;
33     }
34 };