求链表的中心节点

#include<iostream>

using namespace std;

class node{

public:

    node():value(0),next(NULL){}

    ~node(){}

    int value;

    node* next;

};///be careful this ;
node* createlist(int a[],int n)

{

 node* startnode = new node[n];

 node* ret = startnode;

 for(int i = 0;i<n;i++)

 {

     startnode[i].value = a[i];

     if(i<n-1)

         startnode[i].next = startnode + i + 1;

 }

 while(startnode)

 {

     cout<<" "<<startnode->value;

     startnode = startnode->next;

 }

 cout<<endl;

 return ret;

}
void helper(node* head)

{

  node* temp = head;

  while(head->next != NULL && head->next->next != NULL)

  {

      head = head->next->next;

      temp = temp->next;

  }

  cout<<temp->value; ///如果是奇数个，就是中间，如果是偶数个，指向第一个

}
int main()

{

    int a[] = {1,2,3,4,5,6,7,8,9};

    node * t = createlist(a,8);

    helper(t);
}

求链表的中心节点