找出链表中倒数第 k 个结点

 /*
 题目:输入一个单向链表,输出该链表中倒数第 k 个结点。链表的倒数第 0 个结点为链表
 的尾指针。
 链表结点定义如下:
 struct node
 {
     int data;
     struct node *next;
 };
 typedef struct node* PtrToNode;
 typedef PtrToNode Position;
 typedef Position List;
 */
 #include <iostream>
 #include <assert.h>
 #include "./List.h"
 using namespace std;
 void print_list(List list)
 {
     assert(list != NULL);
     list = First(list);
     while(list != NULL)
     {
         cout<<list->data<<" ";
         list = list->next;
     }
     cout<<endl;
 }
 Position get_last_kth(List list, int k)
 {
     assert(list != NULL);
     Position tmp = First(list);
     while(tmp != NULL && --k >= )
         tmp = tmp->next;
     if(NULL == tmp)//the length of list <= k
         return NULL;
     Position ret = First(list);
     while(tmp != NULL)
     {
         ret = ret->next;
         tmp = tmp->next;
     }
     return ret;
 }
 int main(int argc, char const *argv[])
 {
     List list = CreateEmptyList();
     int k;
     for(int i = ; i != ; ++i)
         PushBack(i, list);
     print_list(list);
     while(cin>>k)
     {
         Position tmp = get_last_kth(list, k);
         cout<<"k:"<<k<<" = ";
         if(tmp == NULL)
             cout<<"NULL";
         else
             cout<<tmp->data;
         cout<<endl;
     }
     return ;
 }