遍历BST时出现Stackoverflow异常

我在c++中实现了一个基于链接的BST(二叉搜索树)。我已经写了整个类，一切都很好，但我的作业要求我绘制运行时间:

a.  A sorted list of 50000, 75000, and 100000 items
b.  A random list of 50000, 75000, and 100000 items

很好，我可以插入数字，但它也要求我调用树上的FindHeight()和CountLeaves()方法。我的问题是，我已经实现了两个功能使用recursion。因为我有一个这么大的数字列表，我正在得到一个stackoverflow异常。

这是我的类定义:

template <class TItem>
class BinarySearchTree
{
public:
    struct BinarySearchTreeNode
    {
    public:
        TItem Data;
        BinarySearchTreeNode* LeftChild;
        BinarySearchTreeNode* RightChild;
    };
    BinarySearchTreeNode* RootNode;
    BinarySearchTree();
    ~BinarySearchTree();
    void InsertItem(TItem);
    void PrintTree();
    void PrintTree(BinarySearchTreeNode*);
    void DeleteTree();
    void DeleteTree(BinarySearchTreeNode*&);
    int CountLeaves();
    int CountLeaves(BinarySearchTreeNode*);
    int FindHeight();
    int FindHeight(BinarySearchTreeNode*);
    int SingleParents();
    int SingleParents(BinarySearchTreeNode*);
    TItem FindMin();
    TItem FindMin(BinarySearchTreeNode*);
    TItem FindMax();
    TItem FindMax(BinarySearchTreeNode*);
};

FindHeight()实现

template <class TItem>
int BinarySearchTree<TItem>::FindHeight()
{
    return FindHeight(RootNode);
}
template <class TItem>
int BinarySearchTree<TItem>::FindHeight(BinarySearchTreeNode* Node)
{
    if(Node == NULL)
        return 0;
    return 1 + max(FindHeight(Node->LeftChild), FindHeight(Node->RightChild));
}

CountLeaves()实现

template <class TItem>
int BinarySearchTree<TItem>::CountLeaves()
{
    return CountLeaves(RootNode);
}
template <class TItem>
int BinarySearchTree<TItem>::CountLeaves(BinarySearchTreeNode* Node)
{
    if(Node == NULL)
        return 0;
    else if(Node->LeftChild == NULL && Node->RightChild == NULL)
        return 1;
    else
        return CountLeaves(Node->LeftChild) + CountLeaves(Node->RightChild);
}

我试着思考如何在没有递归的情况下实现这两个方法，但我完全被难住了。有人有什么想法吗?