为什么根永不改变，为什么我得到一个错误的访问错误？
问题描述：
我正在做一个任务来创建一个自我排序二叉搜索树每次重复元素试图插入树时重新组织自己。我遇到了一些我需要帮助解决的错误。为什么根永不改变，为什么我得到一个错误的访问错误？
首先，树的根永远不会改变（我假设问题出在RotateLeft或RotateRight方法）我有一个示例文件，我正在阅读和当通过代码行走时，它似乎相应地组织一切，但是当第一个副本进来时，根永远不会变成现在更高的优先级节点。
我得到的第二个错误是一个不良的访问错误（我注意到它在下面的代码中），我猜也是来自其中一个旋转方法。
#ifndef SelfOrganizingTree_SOBTree_h
#define SelfOrganizingTree_SOBTree_h
#include "BinaryNode.h"
#include "bst.h"
template <class T>
class BinaryNode;
template <class T>
class SOBTree: public BinarySearchTree<T> {
public:
SOBTree();
void insert(const T& x);
void remove(const T& x);
bool isEmpty() const;
void printTree() const;
int reportComparisonCount();
double reportCPUTime();
private:
void insert(const T & x, BinaryNode<T> * & t , BinaryNode<T> * & rootNode);
void RotateRight(BinaryNode<T> * & root);
void RotateLeft(BinaryNode<T> * & root);
void printTree(BinaryNode<T> *t) const;
BinaryNode<T> *root;
void balance (BinaryNode<T> * & root);
};
template <class T >
SOBTree<T> :: SOBTree()
{
root = NULL;
}
/**
* Insert x into the tree
*/
template <class T >
void SOBTree<T > :: insert(const T & x)
{
insert(x, root , root);
}
/**
* Internal method to insert into a subtree.
* x is the item to insert.
* t is the node that roots the subtree.
* Set the new root of the subtree.
*/
template <class T>
void SOBTree<T> :: insert(const T & x, BinaryNode<T> * & t , BinaryNode<T> * & rootNode)
{
// BinaryNode<T> *current = t;
if(t == NULL){
t = new BinaryNode<T>(x, NULL, NULL, rootNode);
//cout << t->element << endl;
t->priority++;
}
else if(x < t->element){
//cout << "left" << endl;
insert(x, t->left , t);
}
else if(t->element < x){
//cout << "right" << endl;
insert(x, t->right , t);
}
else{
//cout << "match found" << endl;
t->priority++; // Duplicate; rotate right or left if priority is higher than the root
balance(t);
}
}
template <class T>
void SOBTree<T>::balance (BinaryNode<T> * & rootN){
cout << "root: " << root->element << endl;
if (rootN->parent && rootN->priority > rootN->parent->priority) { //THIS IS WHERE THE BAD ACCESS ERROR IS BEING THROWN
if (rootN->parent->left == rootN) {
RotateLeft(rootN->parent);
balance(rootN->parent);
}else if (rootN->parent->right == rootN){
RotateRight(rootN->parent);
balance(rootN->parent);
}
}
}
template <class T>
void
SOBTree<T>::RotateLeft(BinaryNode<T> * & rootN) {
/*
Let P be Q's left child.
Set P to be the new root.
Set Q's left child to be P's right child.
Set P's right child to be Q.
*/
BinaryNode<T> * oldRoot = rootN;
// perform rotation
rootN = rootN->left;
oldRoot->left = rootN->right;
rootN->right= oldRoot;
}
template <class T>
void
SOBTree<T>::RotateRight(BinaryNode<T> * & rootN) {
/*
Let Q be P's right child.
Set Q to be the new root.
Set P's right child to be Q's left child.
Set Q's left child to be P.
*/
BinaryNode<T> * oldRoot = rootN;
// perform rotation
rootN = rootN->right;
oldRoot->right = rootN->left;
rootN->left = oldRoot;
}
template <class T>
bool SOBTree<T> :: isEmpty() const
{
return root == NULL;
}
/**
* Print the tree contents in sorted order.
*/
template <class T>
void SOBTree<T> :: printTree() const
{
if(isEmpty())
cout << "Empty tree" << endl;
else
printTree(root);
}
template <class T>
void SOBTree<T> :: printTree(BinaryNode<T> *t) const
{
if(t != NULL)
{
printTree(t->left);
cout << t->element << endl;
printTree(t->right);
}else
return;
}
#endif
下面是BinaryNode结构代码：
template <class Type>
class BinarySearchTree; //forward declaration so BinaryNode knows about BinarySearchTree
template <class Type>
class BinaryNode{
public:
Type element;
BinaryNode<Type>* left;
BinaryNode<Type>* right;
BinaryNode<Type>* parent;
int priority;
BinaryNode(Type theElement, BinaryNode *lt, BinaryNode* rt, BinaryNode *par = NULL, int pri = 0) :
element(theElement), left(lt), right(rt) , parent(par), priority(pri)
{ }
friend class BinarySearchTree<Type>;
};
有谁看到任何东西，我可以改变，以帮帮忙？
答
if (rootN->parent && rootN->priority > rootN->parent->priority) {
要么rootN或rootN->parent是NULL或以其他方式无效的指针。
为什么downvote？ – OghmaOsiris 2012-03-21 19:51:15