数据结构(二叉树的插入与删除) 400 请求报错 

定义一个10个元素(25,12,10,15,55,60,45,70,11,13)的数组以二叉树结构存储,在排序过后删除其中任意元素,删除55的过程中出错,请大家帮忙看看问题,谢谢...

//Tree.h

#include<iostream>
using namespace std;
#ifndef TREE_H
#define TREE_H

template<class T>
class Tree
{
public:
	Tree();
	bool insert(const T& x);
	bool search(const T& x) const;
	bool deleteItem(const T& x);
	void display() const;
private:
	struct TreeNode
	{
		T item;
		TreeNode* left;
		TreeNode* right;
	};
	TreeNode* root;
	bool insert(TreeNode*& aroot,const T& x);
	bool search(TreeNode* aroot,const T& x) const;
	bool deleteItem(TreeNode*& aroot,const T& x);
	void display(TreeNode* aroot) const;
};
#endif

template<class T>
Tree<T>::Tree()
{
	root = NULL;
}

template<class T>
bool Tree<T>::insert(const T& x)
{
	return insert(root,x);
}

template<class T>
bool Tree<T>::search(const T& x) const
{
	return search(root,x);
}

template<class T>
bool Tree<T>::deleteItem(const T& x)
{
	return deleteItem(root,x);
}

template<class T>
void Tree<T>::display() const
{
	display(root);
	cout << endl;
}

template<class T>
bool Tree<T>::insert(TreeNode*& aroot, const T& x)
{
	if(aroot == NULL)
	{
		aroot = new TreeNode;
		aroot -> left = NULL;
		aroot -> right = NULL;
		aroot -> item = x;
		return true;
	}
	else if(aroot -> item == x)
	{
		cout << "元素已存在!" << endl;
		return false;
	}
	else if(aroot -> item > x)
		return insert(aroot -> left,x);
	else
		return insert(aroot -> right,x);
}

template<class T>
bool Tree<T>::search(TreeNode* aroot, const T& x) const
{
	if(aroot == NULL)
	{
		cout << "未找到" << endl;
		return false;
	}
	else if(aroot -> item == x)
	{
		cout << "已找到!" << endl;
		return true;
	}
	else if(aroot -> item > x)
		return search(aroot -> left,x);
	else
		return search(aroot -> right,x);
}

template<class T>
bool Tree<T>::deleteItem(TreeNode*& aroot, const T& x)
{
	if(aroot == NULL)
	{
		cout << "没有要删除的元素!" << endl;
		return false;
	}
	else if(aroot != NULL && aroot -> item == x)
	{
		TreeNode* oldNode = aroot;
		if(aroot -> left == NULL)
		{
			if(aroot -> right == NULL)
			{
				aroot = NULL;
				oldNode = NULL;
				delete aroot;
				delete oldNode;
				return true;
			}
			else
			{	
				oldNode = NULL;
				aroot = aroot -> right;
				aroot -> right = aroot -> right;
				delete oldNode;
				return true;
			}
		}
		else if(aroot -> right == NULL)
		{
			if(aroot -> left == NULL)
			{
				aroot = NULL;
				oldNode = NULL;
				delete oldNode;
				delete aroot;
				return true;
			}
			else
			{
				oldNode = NULL;
				aroot = aroot -> left;
				aroot -> left = aroot -> left;
				delete oldNode;
				return true;
			}
		}
		else 
		{
			TreeNode* newNode = aroot;
			oldNode = NULL;
			aroot = aroot -> left;
			aroot -> left = aroot -> left;
			aroot -> right = aroot -> right;
			if(newNode -> right != NULL)
				aroot -> right -> right = newNode -> right;
			delete oldNode;
			return true;
		}
	}
	else if(aroot -> item > x)
		return deleteItem(aroot -> left,x);
	else
		return deleteItem(aroot -> right,x);
}

template<class T>
void Tree<T>::display(TreeNode *aroot) const
{
	if(aroot != NULL)
	{
		display(aroot -> left);
		cout << aroot -> item << " ";
		display(aroot -> right);
	}
}

//Tree.cpp

#include<iostream>
#include"Tree.h"
using namespace std;

typedef Tree<int> Treelist;
int main()
{
	Treelist tl;
	int a[10] = {25,12,10,15,55,60,45,70,11,13};

	for(int i = 0;i < 10;i++)
		tl.insert(a[i]);
	tl.display();
	tl.deleteItem(12);
	tl.display();
	system("pause");
	return 0;
}