在二叉树中求位于先序序列中第k个位置的结点的值

编写递归算法，在二叉树中求位于先序序列中第k个位置的结点的值。

二叉链表类型定义：

typedef struct BiTNode {
    TElemType data;
    BiTNode  *lchild, *rchild;
} BiTNode, *BiTree;

实现函数如下：

TElemType GetElemType(BiTree bt,int &num,TElemType &e){
    if(bt){
        if(num == 1){
            e = bt -> data;
            return 0;
        }else{
            if(bt -> lchild){
                --num;
                GetElemType(bt -> lchild, num, e);
            }
            if(bt -> rchild){
                --num;
                GetElemType(bt -> rchild, num, e);
            }
        }
    }
}
TElemType PreOrder(BiTree bt, int k)
/* bt is the root node of a binary linked list, */
/* Preorder travel it and find the node whose   */
/* position number is k, and return its value.  */
/* if can't found it, then return '#'.          */
{
    TElemType e;
    e = '#';
    GetElemType(bt, k, e);
    return e;
}