可以用递归啊 
按书上的算法自己写 有问题再问啊

bitree *CREATREE()                                 /*生成二叉树*/
{ char ch;
  int front,rear;
  bitree *root,*s;
  root=NULL;
  front=1;rear=0;
  ch=getchar();
  while(ch!='$')
  { s=NULL;
    if(ch!='@')
    {
        s=malloc(sizeof(bitree));
        s->data=ch;
        s->lchild=NULL;
        s->rchild=NULL;
    }
    rear++;
    Q[rear]=s;
    if(rear==1) root=s;
    else
    {
        if(s&&Q[front])
            if(rear%2==0) Q[front]->lchild=s;
            else
                Q[front]->rchild=s;
        if(rear%2==1) front++;
    }
    ch=getchar();
  }
  return root;
}