访问权限冲突怎么修改

BiTreeNode.h
#pragma once
#include
using namespace std;

template<class T>
class BiTreeNode
{
private:
    BiTreeNode<T>* leftChild;
    BiTreeNode<T>* rightChild;
public:
    T data;
    BiTreeNode():leftChild(NULL),rightChild(NULL){}
    BiTreeNode(T item, BiTreeNode<T>* left = NULL, BiTreeNode<T>* right = NULL ):data(item),leftChild(left),rightChild(right){}
    ~BiTreeNode(){}
    BiTreeNode<T>*& Left() { return leftChild; }
    BiTreeNode<T>*& Right() { return rightChild; }
};

BiTreeLib.h
#pragma once
#include"BiTreeNode.h"

//构造二叉树
template <class T>
BiTreeNode<T>* GetTreeNode(const T item, BiTreeNode<T>* left = NULL, BiTreeNode<T>* right = NULL)
{
    BiTreeNode* p = new BiTreeNode(item, left, right);
    return p;
}

//前序遍历
template <class T>
void PreOrder(BiTreeNode<T>* t, void Visit(T item))
{
    if (t != NULL)
    {
        Visit(t->data);
        PreOrder(t->Left(), Visit);
        PreOrder(t->Right(), Visit);
    }
}

//中序遍历
template <class T>
void InOrder(BiTreeNode<T>* t, void Visit(T item))
{
    if (t != NULL)
    {
        InOrder(t->Left(), Visit);
        Visit(t->data);
        InOrder(t->Right(), Visit);
    }
}

//后序遍历
template <class T>
void PostOrder(BiTreeNode<T>* t, void Visit(T item))
{
    if (t != NULL)
    {
        PostOrder(t->Left(), Visit);
        PostOrder(t->Right(), Visit);
        Visit(t->data);
    }
}

//后序遍历实现撤销
template <class T>
void Destroy(BiTreeNode<T>*& root)
{
    if (root != NULL && root->Left != NULL)
    {
        Destroy(root->Left());
    }
    if (root != NULL && root->Right!= NULL)
    {
        Destroy(root->Right());
    }
    //cout << root->data << " ";
    delete root;
}

//打印
template<class T>
void PrintBiTree(BiTreeNode<T>*& root, int level)
{
    if (root != NULL)
    {
        PrintBiTree(root->Right(), level + 1);
        if (level != 0)
        {
            for (int i = 0; i < 6 * (level - 1) ; i++)
            {
                cout << " ";
            }
            cout << "----";
        }
        PrintBiTree(root->Left(), level + 1);
    }
}

//查找
template<class T>
BiTreeNode<T>* Search(BiTreeNode<T>* t, T x)
{
    BiTreeNode* p;
    if (t == NULL)
    {
        return NULL;
    }
    if (t->data == x)
    {
        return t;
    }
    if (t->Left() != NULL)
    {
        p = Search(t->Left(), x);
        if (p != NULL)
        {
            return p;
        }
    }
    if (t->Right() != NULL)
    {
        p = Search(t->Right(), x);
        if (p != NULL)
        {
            return p;
        }
    }
    return NULL;//查找失败
}

SeqStack.h
#pragma once
#include
using namespace std;
typedef BiTreeNode<char> DataType;
const int MaxStackSize = 100;

class SeqStack
{
private:
    DataType *data[MaxStackSize];
    int top;
public:
    SeqStack();
    ~SeqStack();
    void Push( DataType *item);
    DataType *Pop();
    DataType *GetTop()const;
    bool NotEmpty()const;
};

SeqStack::SeqStack() { top = 0; };
SeqStack::~SeqStack() {}

//入栈
void SeqStack::Push( DataType *item)
{
    if (top == MaxStackSize)
    {
        cout << "堆栈已满" << endl;
        exit(0);
    }
    else
    {
        data[top] = item;
        top++;
    }
}

//出栈
DataType *SeqStack::Pop()
{
    if (top == 0)
    {
        cout << "堆栈已空" << endl;
        exit(0);
    }
    else
    {
        top--;
        return data[top];
    }
}

//取栈顶元素
DataType *SeqStack::GetTop()const
{
    if (top == 0)
    {
        cout << "堆栈空" << endl;
        exit(0);
    }
    return data[top - 1];
}

//判断是否非空
bool SeqStack::NotEmpty()const
{
    if (top != 0)
    {
        return true;
    }
    else
    {
        return false;
    }
}

#include"SeqStack.h"


void MakeCharBiTree(BiTreeNode<char>*& root)
{
    BiTreeNode<char>*a,* b, * c, * d, * e, * f, * g, * null = NULL;
    g = GetTreeNode('G', null, null);
    d = GetTreeNode('D', null, g);
    b = GetTreeNode('B', d, null);
    e = GetTreeNode('E', null, null);
    f = GetTreeNode('F', null, null);
    c = GetTreeNode('C', e, f);
    a = GetTreeNode('A', b, c);
}
void Print(char item)
{
    cout << item << " ";
}
//非递归
void NotRecurPreOrder(DataType* t, void Visit(char item))
{
    SeqStack stack;
    DataType* p;
    stack.Push(t);
    while (stack.NotEmpty())
    {
        p = stack.Pop();
        Visit(p->data);
        if (p->Right() != NULL)
        {
            stack.Push(p->Right());
        }
        if (p->Left() != NULL)
        {
            stack.Push(p->Left());
        }
    }
}

int main()
{
    BiTreeNode<char>* root1;
    MakeCharBiTree(root1);
    cout << "递归：";
    PreOrder(root1, Print);
}

在前序遍历中引发访问权限冲突，请问是什么问题，怎么修改

MakeCharBiTree函数的参数root有啥用？函数代码跟它似乎没有关系啊