数据结构与算法（C语言版）__红黑树04

我们今天把双旋转加到红黑树里面，单旋转有的时候不能让二叉查找树平衡，所以需要调用双旋转。双旋转就是把两个单旋转放在一起形成双旋转。

在头文件中加入Except.h和RedBlackTree.h，在源文件中加入TestRedBlackTree.cpp

//Except.h#ifndef EXCEPT_H#define EXCEPT_H#include<string>using namespace std;class DSException{public:    DSException(const string & msg = "") :message(msg){}    virtual ~DSException(){}    virtual string toString() const{        return "Exception " + string(":") + what();    }    virtual string what() const{        return message;    }private:    string message;};class DuplicateItemException :public DSException{public:    DuplicateItemException(const string & msg = "") :DSException(msg){}};#endif

//RedBlackTree.h//红黑树主要程序#ifndef RED_BLACK_TREE_H_#define RED_BLACK_TREE_H_#include"Except.h"template<class Comparable>class RedBlackTree;template<class Comparable>class RedBlackNode;template<class Comparable>class RedBlackTree{public:    RedBlackTree(const Comparable & negInf);//红黑树的构造函数    ~RedBlackTree();    enum{RED,BLACK};    void insert(const Comparable & x);    typedef RedBlackNode<Comparable> Node;//private:为了测试，临时变成公有的public:    Node *header;    Node *nullNode;    Node *current;//当前节点    Node *parent;//父结点    Node *grand;//祖父节点    Node *great;//曾祖父节点    void rotateWithLeftChild(Node * & k2) const;    void rotateWithRightChild(Node * & k1) const;    void doubleRotateWithLeftChild(Node * & k3)const;    void doubleRotateWithRightChild(Node * & k4)const;};template<class Comparable>class RedBlackNode{//private:为了测试，临时变成publicpublic:    Comparable element;    RedBlackNode *left;    RedBlackNode *right;    int color;    RedBlackNode(const Comparable & theElement = Comparable(),        RedBlackNode *lt = NULL,        RedBlackNode *rt = NULL,        int c = RedBlackTree<Comparable>::BLACK)        :element(theElement), left(lt), right(rt), color(c){}    friend class RedBlackTree<Comparable>;};template<class Comparable>RedBlackTree<Comparable>::RedBlackTree(const Comparable & negInf){    nullNode = new Node();    nullNode->left = nullNode->right = nullNode;    header = new Node(negInf);    header->left = header->right = nullNode;}template<class Comparable>RedBlackTree<Comparable>::~RedBlackTree(){    delete nullNode;    delete header;}template<class Comparable>void RedBlackTree<Comparable>::insert(const Comparable & x){    current = parent = grand = header;    nullNode->element = x;    while (current->element != x){        great = grand; grand = parent; parent = current;        current = x < current->element ? current->left : current->right;    }    if (current != nullNode)        throw DuplicateItemException();    current = new Node(x, nullNode, nullNode);    if (x < parent->element)        parent->left = current;    else        parent->right = current;    //自动平衡 -> 红黑树}template<class Comparable>void RedBlackTree<Comparable>::rotateWithLeftChild(Node * & k2)const{    Node *k1 = k2->left;    k2->left = k1->right;//横向移动    k1->right = k2;    k2 = k1;}template<class Comparable>void RedBlackTree<Comparable>::rotateWithRightChild(Node * & k1)const{    Node *k2 = k1->right;    k1->right = k2->left;    k2->left = k1;    k1 = k2;}template<class Comparable>//双旋转_向右旋转void RedBlackTree<Comparable>::doubleRotateWithLeftChild(Node * & k3)const{    rotateWithRightChild(k3->left);    rotateWithLeftChild(k3);}template<class Comparable>//双旋转_向左旋转void RedBlackTree<Comparable>::doubleRotateWithRightChild(Node * & k4)const{    rotateWithLeftChild(k4->right);    rotateWithRightChild(k4);}#endif

//TestRedBlackTree.cpp#include<iostream>#include"RedBlackTree.h"using namespace std;int main(){    cout << "测试红黑树：" << endl;    const int NEG_INF = -99999;//负的无穷大，    RedBlackTree<int> t(NEG_INF);//创建一个空树，    t.insert(12);    t.insert(16);    t.insert(8);    t.insert(10);    t.insert(4);    t.insert(14);    t.insert(2);    t.insert(6);    t.insert(5);    cout << t.header->right->left->left->right->left->element << endl;    cout << "旋转之前：" << endl;    cout << t.header->right->left->element << endl;    cout << "向右双旋转：" << endl;    t.doubleRotateWithLeftChild(t.header->right->left);    cout << t.header->right->left->element << endl;    cout << t.header->right->left->left->right->element << endl;    system("pause");    return 0;}

总结：但旋转不能满足红黑树的需要，所以需要双旋转，使红黑树能够自动平衡二叉查找树。我们做的单旋转和双旋转都是为insert服务的，如果insert里面不能使二叉查找树旋转，那么就是普通的二叉查找树，我在下一个博客里面把旋转加到insert里面，构成真正的红黑树。