printf("\nplease input yuan su:\n");    /*输入二叉树的元素*/
        scanf("%c",&ch);
if(ch=='*') T=NULL;
        else {
if(!(T=(BTN *)malloc(sizeof(BTN)))) exit(OVERFLOW);
        T->data=ch;
        CreateBT(T->lchild);
        CreateBT(T->rchild);
}




这个二叉树元素怎么输入啊举个例子