二叉搜索树实现(c++)

大部分代码来自Weiss的"c++中的数据结构和算法分析"，在我在CodeBlock(gnu,gcc)上键入代码后，编译器报告没有错误，但随后我试图创建一个实例并测试一些函数，它出错了。BST()或insert()似乎有问题，因为程序在运行后立即卡住。有人能帮我找出解决这个问题的方法吗?好谢谢! !

#include <iostream>
using namespace std;
struct TreeNode
{
    int element;
    TreeNode*left,*right;
    TreeNode(const int&e,TreeNode*le=NULL,TreeNode*rt=NULL):element(e),left(le),right(rt){};
};
class BST
{
public:
    BST(){root=NULL;};
    ~BST(){ makeEmpty(root); };
// use public member function to call private member functions.
    void insert(const int & x){ insert(x, root); }
    void remove(const int & x){ remove(x, root); }
    TreeNode*findMin() const{ return findMin(root); }
    bool contain(const int & x) const{ return contain(x,root); }
    void printNodes() const{ printNodes(root); }
private:
    TreeNode*root;
    void makeEmpty(TreeNode*&);
    TreeNode* findMin(TreeNode*) const;
    void insert(const int &, TreeNode*) const;
    void remove(const int &, TreeNode*) const;
    bool contain(const int &, TreeNode*) const;
    void printNodes(TreeNode*) const;
};
void BST::makeEmpty(TreeNode*&t)
{
    if(t!=NULL)
    {
        makeEmpty(t->left);
        makeEmpty(t->right);
        delete t;
    }
    t=NULL;
}
TreeNode* BST::findMin(TreeNode*t) const
{
    if(t->left==NULL)    return t;
    return findMin(t->left);
}
void BST::insert(const int & x, TreeNode* t) const
{
    if(t==NULL) t=new TreeNode(x,NULL,NULL);
    else if(x < t->element)    insert(x,t->left);
    else if(x > t->element)    insert(x,t->right);
    else;   /// duplicate, do nothing
}
void BST::remove(const int & x, TreeNode* t) const
{
    if(t==NULL) return;
    if(t->element > x)    remove(x, t->left);
    else if(t->element < x)  remove(x, t->right);
    else if(t->left!=NULL && t->right!=NULL)
    {
        t->element=findMin(t->right)->element;
        remove(t->element,t->right);
    }
    else
    {
        TreeNode*oldNode=t;
        t=(t->left==NULL)?t->right:t->left;
        delete oldNode;
    }
}
bool BST::contain(const int & x, TreeNode*t) const
{
    if(t==NULL)    return false;
    else if(x<t->element)    return contain(x,t->left);
    else if(x>t->element)    return contain(x,t->right);
    else    return true;
}
void BST::printNodes(TreeNode*t) const
{
    if(t==NULL) return;
    cout<<t->element<<" ";
    printNodes(t->left);
    printNodes(t->right);
    cout<<endl;
};

int main()
{
    BST BinarySearchTree;
    int element,node;
    for(int i=0; i<5; i++)
    {
        cin>>element;
        BinarySearchTree.insert(element);
    }
    BinarySearchTree.printNodes();
    cout<<BinarySearchTree.findMin()->element<<endl;
    cin>>node;
    if(BinarySearchTree.contain(node)){ cout<<"item "<<node<<" is in BST."<<endl; }
    BinarySearchTree.remove(node);
    BinarySearchTree.printNodes();
    return 0;
}