一、介绍
1. 概念
- 红黑树,是一种二叉搜索树,但在每个结点上增加一个存储位表示结点的颜色,可以是Red或Black。
- 通过对任何一条从根到叶子的路径上各个结点着色方式的限制,红黑树确保没有一条路径会比其他路径长出俩倍,因而是接近平衡的
2. 性质
- 每个结点不是红色就是黑色
- 根节点是黑色的
- 如果一个节点是红色的,则它的两个孩子结点是黑色的
- 对于每个结点,从该结点到其所有后代叶结点的简单路径上,均包含相同数目的黑色结点
- 每个叶子结点都是黑色的(此处的叶子结点指的是空结点)
3. 结点定义
enum Colour//两种颜色
{RED,BLACK
};//定义红黑树的结点
template<class K, class V>
struct RBTreeNode
{RBTreeNode* _left;RBTreeNode* _right;RBTreeNode* _parent;pair<K, V> _kv;Colour _col;RBTreeNode(const pair<K, V>& kv):_left(nullptr),_right(nullptr),_parent(nullptr),_kv(kv),_col(RED){}
};
二、插入的3种情况
(一)情况1
- 因为cur为当前插入新结点(红色),而不能有连在一起的红色节点,所以parent结点需要变成黑色。
- 控制每条路径上黑节点的数量相同,那么就要把uncle变黑
- grandparent如果不是根节点,需要继续向上调整,所以grandparent需要变成红色
//情况1:uncle存在且为红色
if (uncle != nullptr && uncle->_col == RED)
{//调整颜色parent->_col = uncle->_col = BLACK;grandfather->_col = RED;//继续往上调整cur = grandfather;parent = cur->_parent;
}
(二)情况2
//情况2
if (cur == parent->_left)
{// grandfather// parent// curRotateR(grandfather);//右旋转//调整颜色parent->_col = BLACK;grandfather->_col = RED;}
(三)情况3
else//cur在parent的右边
{// grandfather// parent// curRotateL(parent);//先左旋转RotateR(grandfather);//再右旋转//调整颜色cur->_col = BLACK;grandfather->_col = RED;
}
(四)插入代码
bool Insert(const pair<K, V>& kv)
{if (_root == nullptr)//如果开始结点为空{_root = new Node(kv);_root->_col = BLACK;//根节点为黑色return true;}Node* parent = nullptr;Node* cur = _root;//寻找应该插入的位置while (cur){if (cur->_kv.first < kv.first){parent = cur;cur = cur->_right;}else if (cur->_kv.first > kv.first){parent = cur;cur = cur->_left;}else//已经存在一样的值,直接返回false{return false;}}//链接cur = new Node(kv);cur->_col = RED;if (parent->_kv.first < kv.first){parent->_right = cur;cur->_parent = parent;}else{parent->_left = cur;cur->_parent = parent;}//调整while (parent && parent->_col == RED)//如果父亲结点是黑色直接结束{Node* grandfather = parent->_parent;if (parent == grandfather->_left){// grandfather// parent uncle// cur//Node* uncle = grandfather->_right;//情况1:uncle存在且为红色if (uncle != nullptr && uncle->_col == RED){//调整颜色parent->_col = uncle->_col = BLACK;grandfather->_col = RED;//继续往上调整cur = grandfather;parent = cur->_parent;}else//uncle不存在或者uncle为黑色{ //情况2if (cur == parent->_left){// grandfather// parent// curRotateR(grandfather);//右旋转//调整颜色parent->_col = BLACK;grandfather->_col = RED;}else//cur在parent的右边{// grandfather// parent// curRotateL(parent);//先左旋转RotateR(grandfather);//再右旋转//调整颜色cur->_col = BLACK;grandfather->_col = RED;}break;}}else//parent == grandfather->_right{Node* uncle = grandfather->_left;// g// u p// c////情况1:uncle存在且为红色if (uncle != nullptr && uncle->_col == RED){//调整颜色parent->_col = uncle->_col = BLACK;grandfather->_col = RED;//继续往上调整cur = grandfather;parent = cur->_parent;}else//uncle不存在或者uncle为黑色{if (cur == parent->_right){// g// p// cRotateL(grandfather);//调整颜色parent->_col = BLACK;grandfather->_col = RED;}else{// g// p// cRotateR(parent);//先右旋RotateL(grandfather);//再左旋//调整颜色cur->_col = BLACK;grandfather->_col = RED;}break;}}}_root->_col = BLACK;return true;
}
三、判断是否近似平衡
// // 根节点->当前节点这条路径的黑色节点的数量
bool Check(Node* root, int blacknum, const int refVal)
{if (root == nullptr)//走到了一条路径的尽头{if (blacknum != refVal){cout << "存在黑色节点数量不相等的路径" << endl;return false;}return true;}if (root->_col == RED && root->_parent->_col == RED){cout << "有连续的红色节点" << endl;return false;}if (root->_col == BLACK){++blacknum;}return Check(root->_left, blacknum, refVal)&& Check(root->_right, blacknum, refVal);
}bool IsBalance()//判断是否平衡
{if (_root == nullptr)return true;if (_root->_col == RED)//根结点如果是红色return false;int refVal = 0;Node* cur = _root;while (cur)//计算其中一条路径上的黑色节点数量作为参考值{if (cur->_col == BLACK){++refVal;}cur = cur->_left;}int blacknum = 0;return Check(_root, blacknum, refVal);
}
四、完整代码
#pragma once
#include<iostream>
#include<vector>
#include<string>
using namespace std;
enum Colour//两种颜色
{RED,BLACK
};//定义红黑树的结点
template<class K, class V>
struct RBTreeNode
{RBTreeNode* _left;RBTreeNode* _right;RBTreeNode* _parent;pair<K, V> _kv;Colour _col;RBTreeNode(const pair<K, V>& kv):_left(nullptr),_right(nullptr),_parent(nullptr),_kv(kv),_col(RED){}
};template<class K, class V>
class RBTree
{typedef RBTreeNode<K, V> Node;
public:bool Insert(const pair<K, V>& kv){if (_root == nullptr)//如果开始结点为空{_root = new Node(kv);_root->_col = BLACK;//根节点为黑色return true;}Node* parent = nullptr;Node* cur = _root;//寻找应该插入的位置while (cur){if (cur->_kv.first < kv.first){parent = cur;cur = cur->_right;}else if (cur->_kv.first > kv.first){parent = cur;cur = cur->_left;}else//已经存在一样的值,直接返回false{return false;}}//链接cur = new Node(kv);cur->_col = RED;if (parent->_kv.first < kv.first){parent->_right = cur;cur->_parent = parent;}else{parent->_left = cur;cur->_parent = parent;}//调整while (parent && parent->_col == RED)//如果父亲结点是黑色直接结束{Node* grandfather = parent->_parent;if (parent == grandfather->_left){// grandfather// parent uncle// cur//Node* uncle = grandfather->_right;//情况1:uncle存在且为红色if (uncle != nullptr && uncle->_col == RED){//调整颜色parent->_col = uncle->_col = BLACK;grandfather->_col = RED;//继续往上调整cur = grandfather;parent = cur->_parent;}else//uncle不存在或者uncle为黑色{ //情况2if (cur == parent->_left){// grandfather// parent// curRotateR(grandfather);//右旋转//调整颜色parent->_col = BLACK;grandfather->_col = RED;}else//cur在parent的右边{// grandfather// parent// curRotateL(parent);//先左旋转RotateR(grandfather);//再右旋转//调整颜色cur->_col = BLACK;grandfather->_col = RED;}break;}}else//parent == grandfather->_right{Node* uncle = grandfather->_left;// g// u p// c////情况1:uncle存在且为红色if (uncle != nullptr && uncle->_col == RED){//调整颜色parent->_col = uncle->_col = BLACK;grandfather->_col = RED;//继续往上调整cur = grandfather;parent = cur->_parent;}else//uncle不存在或者uncle为黑色{if (cur == parent->_right){// g// p// cRotateL(grandfather);//调整颜色parent->_col = BLACK;grandfather->_col = RED;}else{// g// p// cRotateR(parent);//先右旋RotateL(grandfather);//再左旋//调整颜色cur->_col = BLACK;grandfather->_col = RED;}break;}}}_root->_col = BLACK;return true;}// 根节点->当前节点这条路径的黑色节点的数量bool Check(Node* root, int blacknum, const int refVal){if (root == nullptr)//走到了一条路径的尽头{if (blacknum != refVal){cout << "存在黑色节点数量不相等的路径" << endl;return false;}return true;}if (root->_col == RED && root->_parent->_col == RED){cout << "有连续的红色节点" << endl;return false;}if (root->_col == BLACK){++blacknum;}return Check(root->_left, blacknum, refVal)&& Check(root->_right, blacknum, refVal);}bool IsBalance()//判断是否平衡{if (_root == nullptr)return true;if (_root->_col == RED)//根结点如果是红色return false;int refVal = 0;Node* cur = _root;while (cur)//计算其中一条路径上的黑色节点数量作为参考值{if (cur->_col == BLACK){++refVal;}cur = cur->_left;}int blacknum = 0;return Check(_root, blacknum, refVal);}void RotateL(Node* parent)//左单旋{Node* parentParent = parent->_parent;Node* subR = parent->_right;Node* subRL = subR->_left;parent->_right = subRL;subR->_left = parent;//更新调整结点的父指针指向parent->_parent = subR;//subRL->_parent = parent;错误,没有判断subRL是不是为空if (subRL != nullptr){subRL->_parent = parent;}if (_root == parent){_root = subR;subR->_parent = nullptr;}else{if (parentParent->_left == parent){parentParent->_left = subR;}else{parentParent->_right = subR;}subR->_parent = parentParent;}//更新平衡因子//parent->_bf = subR->_bf = 0;}void RotateR(Node* parent)//右单旋{Node* parentParent = parent->_parent;Node* subL = parent->_left;Node* subLR = subL->_right;parent->_left = subLR;//更新调整结点的父指针指向if (subLR != nullptr){subLR->_parent = parent;}subL->_right = parent;//更新调整结点的父指针指向parent->_parent = subL;if (_root == parent){_root = subL;subL->_parent = nullptr;}else{//需要先判断subR应该链接在parentParent的哪一侧if (parentParent->_left == parent){parentParent->_left = subL;}else{parentParent->_right = subL;}subL->_parent = parentParent;}//更新平衡因子//parent->_bf = subL->_bf = 0;}void InOrder()//中序遍历{_InOrder(_root);cout << endl;}void _InOrder(Node* root)//中序遍历{if (root == nullptr){return;}_InOrder(root->_left);cout << root->_kv.first << " ";_InOrder(root->_right);}int Height(){return _Height(_root);}int _Height(Node* root){if (root == nullptr)return 0;int leftHeight = _Height(root->_left);int rightHeight = _Height(root->_right);return leftHeight > rightHeight ? leftHeight + 1 : rightHeight + 1;}size_t Size(){return _Size(_root);}size_t _Size(Node* root){if (root == NULL)return 0;return _Size(root->_left)+ _Size(root->_right) + 1;}Node* Find(const K& key){Node* cur = _root;while (cur){if (cur->_kv.first < key){cur = cur->_right;}else if (cur->_kv.first > key){cur = cur->_left;}else{return cur;}}return NULL;}
private:Node* _root = nullptr;
};
1. 测试用例1
#include"RBTree.h"
int main()
{//int a[] = { 16, 3, 7, 11, 9, 26, 18, 14, 15 };//int a[] = { 4, 2, 6, 1, 3, 5, 15, 7, 16, 14 };int a[] = { 790,760,969,270,31,424,377,24,702 };RBTree<int, int> t;for (auto e : a){if (e == 702){int i = 0;}cout << "Insert:" << e << "->";t.Insert(make_pair(e, e));cout << t.IsBalance() << endl;}t.InOrder();cout << t.IsBalance() << endl;return 0;
}
2. 测试用例2
#include"RBTree.h"int main()
{const int N = 100000;vector<int> v;v.reserve(N);srand(time(0));for (size_t i = 0; i < N; i++){v.push_back(rand() + i);//cout << v.back() << endl;}size_t begin2 = clock();RBTree<int, int> t;for (auto e : v){if (e == 29365){int i = 0;}//cout << "Insert:" << e << "->";t.Insert(make_pair(e, e));//cout << t.IsBalance() << endl;}size_t end2 = clock();cout << "Insert:" << end2 - begin2 << endl;cout << t.IsBalance() << endl;cout << t.Height() << endl;cout << t.Size() << endl;size_t begin1 = clock();for (auto e : v){t.Find(e);}for (size_t i = 0; i < N; i++){t.Find((rand() + i));}size_t end1 = clock();cout << "Find:" << end1 - begin1 << endl;return 0;
}