这是我用C语言编的数据结构程序：目的是通过结构数组来表示二叉树
在编译时说我create_btree 中有非法运算
错误 tree02.c 15: 非法的结构运算在 create_btree 函数中
下面是源程序：请高手帮忙啊！！谢谢了！
#include<stdlib.h>
struct tree
{
  int left;
  int data;
  int right;
};
typedef struct tree treenode;
treenode b_tree[15];
void create_btree(int *b_tree,int *nodelist,int len)
     {
      int i;
      int level;
      int position;
      b_tree[0].data=nodelist[0];/*以第一个节点为根节点*/
         for(i=1;i<len;i++)
         {
          b_tree[i].data=nodelist[i];
          level=0;
          position=0;
            while(position==0)
            { /*判断是左子树或是右子树*/
             if(nodelist[i]>b_tree[level].data)
             /*右树是否还有下一阶层*/
                if(b_tree[level].right!=-1)
                  level=b_tree[level].right;
                else
                position=-1;
              else
                if(b_tree[level].left!=-1)
                  level=b_tree[level].left;
                 else
                   position=1;

             }
             if(position==1)
               b_tree[level].left=i;
             else
                b_tree[level].right=i;

         }

     }
     void main()
     {
       int i,index;
       int data;
       int nodelist[16];
       printf("\nplease input the elements of binary tree(exit for 0):\n");
       index=1;
       scanf("%d",&data);
       while(data!=0)
       {
        nodelist[index]=data;
        index=index+1;
        scanf("%d",&data);
        }
        for(i=0;i<15;i++)
        {
           b_tree[i].data=0;
           b_tree[i].left=-1;
           b_tree[i].right=-1;
        }
        create_btree(nodelist,index)
        {
         printf("\nthe binary tree content:\n");
         printf("   left  data   right\n");
         printf("=======================\n");
         for(i=1;i<15;i++)
         {
         printf("%2d:[%d]   [%d]   [%d] \n",i,
         b_tree[i].left,b_tree[i].data,b_tree[i].right);
         }
        }
        getch();

     }