红黑树
- 一.红黑树简单实现
- 1.性质
- 二.更新颜色
- 1.情况一
- 2.情况二
- 3.情况三
- 3.完整代码(代码有注释,稍微画图很容易理解,旋转部分可以看我的AVL树博客)
- 二.map和set
- 1.基本实现
- 2.迭代器
本篇的前置条件是AVL树的旋转和搜索树,如果不了解可以看看我的AVL树博客
一.红黑树简单实现
1.性质
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。
- 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)。
创建节点
二.更新颜色
1.情况一
插入一个节点,它的父亲是红色的并且它有叔叔且叔叔也是红色的。
2.情况二
如果叔叔不存在
此时单纯的变色是无法解决问题的,需要进行旋转,在此情况是右旋。
3.情况三
叔叔存在且为黑,注意此时插入的点是在最下面,cur经过上面的转变后到达图示的位置。
3.完整代码(代码有注释,稍微画图很容易理解,旋转部分可以看我的AVL树博客)
测试
#include"RBTree.h"
#include<vector>
int main()
{
RBTree<int, int> t;
srand(time(0));
vector<int>a;
for (int i = 0; i < 100; i++)
{
int x = rand();
a.push_back(x);
}
for (auto x : a)
t.Insert(make_pair(x, x));
cout << t.IsBalance() << endl;
return 0;
}
树
#include<iostream>
#include<assert.h>
using namespace std;
enum Color
{
RED,
BLACK
};
template<class K,class V>
struct RBTreeNode
{
pair<K, V> _kv;
RBTreeNode<K, V>* _left;
RBTreeNode<K, V>* _right;
RBTreeNode<K, V>* _parent;
RBTreeNode(const pair<K,V>& kv)//初始化节点
:_kv(kv)
,_left(nullptr)
,_right(nullptr)
,_parent(nullptr)
,_col(RED)
{}
Color _col;
};
template<class K,class V>
class RBTree
{
public:
typedef RBTreeNode<K, V> Node;
bool Insert(const pair<K, V>& kv)
{
if (_root == nullptr)
{
_root = new Node(kv);
_root->_col = BLACK;//根为黑色
return true;
}
Node* parent = _root;
Node* cur = _root;
//一般的搜索二叉树插入
while (cur)
{
if (kv.first > cur->_kv.first)
{
parent = cur;
cur = cur->_right;
}
else if (kv.first < cur->_kv.first)
{
parent = cur;
cur = cur->_left;
}
else
return false;
}
cur = new Node(kv);
cur->_parent = parent;
if (parent->_kv > kv) parent->_left = cur;
else parent->_right = cur;
//进行颜色更新
while (parent && parent->_col == RED)
{
Node* grandparent = parent->_parent;
Node* uncle;
//找到叔叔
if (grandparent->_left == parent)
uncle = grandparent->_right;
else
uncle = grandparent->_left;
//如果叔叔存在且为红色
if (uncle && uncle->_col == RED)
{
//变颜色
parent->_col = uncle->_col = BLACK;
grandparent->_col = RED;
//继续向上
cur = grandparent;
parent = cur->_parent;
}
//如果叔叔不存在或者是黑色
else
{
//parent是左,cur是左,进行右单旋
if (grandparent->_left == parent && parent->_left == cur)
{
RotateR(grandparent);
grandparent->_col = RED;
parent->_col = BLACK;
}
//parent是左,cur是右,进行左右旋
else if (grandparent->_left == parent && parent->_right == cur)
{
RotateL(parent);
RotateR(grandparent);
cur->_col = BLACK;
grandparent->_col = RED;
}
//parent是右,cur是右,进行左单旋
else if (grandparent->_right == parent && parent->_right == cur)
{
RotateL(grandparent);
grandparent->_col = RED;
parent->_col = BLACK;
}
//parent是右,cur是左,进行右左旋
else
{
RotateR(parent);
RotateL(grandparent);
cur->_col = BLACK;
grandparent->_col = RED;
}
}
}
_root->_col = BLACK;
}
//旋转函数
void RotateL(Node* parent)
{
Node* cur = parent->_right;
Node* curleft = cur->_left;
Node* ppnode = parent->_parent;//记录父节点的父节点
//父节点的右孩子变成curleft
parent->_right = curleft;
if (curleft)//细节注意curleft为空时不能操作
curleft->_parent = parent;
//父节点变为cur的左孩子
cur->_left = parent;
parent->_parent = cur;
//如果原来父节点是根节点
if (parent == _root)
{
_root = cur;
cur->_parent = nullptr;
}
else//如果不是根节点判断它应该是左儿子还是右儿子
{
if (ppnode->_left == parent)
{
ppnode->_left = cur;
}
else
{
ppnode->_right = cur;
}
cur->_parent = ppnode;
}
}
void RotateR(Node* parent)
{
Node* cur = parent->_left;
Node* curright = cur->_right;
Node* pphead = parent->_parent;
//父节点到cur右边
cur->_right = parent;
parent->_parent = cur;
//父节点的左孩子变成curright
parent->_left = curright;
if (curright)
curright->_parent = parent;
//cur的父节点变为原来父节点的父节点
if (pphead)//如果不是根节点
{
if (pphead->_left == parent)
pphead->_left = cur;
else
pphead->_right = cur;
cur->_parent = pphead;
}
else
{
_root = cur;
cur->_parent = nullptr;
}
}
void RotateRL(Node* parent)
{
Node* cur = parent->_right;
Node* curleft = cur->_left;
RotateR(parent->_right);
RotateL(parent);
}
void RotateLR(Node* parent)
{
Node* cur = parent->_left;
Node* curright = cur->_right;
RotateL(parent->_left);
RotateR(parent);
}
//测试是否出问题
bool IsBalance()
{
return IsBalance(_root);
}
bool IsBalance(Node* root)
{
//根是否为黑色
if (_root->_col != BLACK)
{
cout << "根不是红色"<<endl;
return false;
}
int blackcheck = 0;
Node* cur = _root;
while (cur)
{
if (cur->_col == BLACK)
blackcheck++;
cur = cur->_left;
}
//判断是否有两个连续的红色和每条路径的黑色是否相同
return CheckColor(_root,blackcheck,0);
}
bool CheckColor(Node*root,int blackcheck,int blacknum)
{
if (root == nullptr)
{
//检查是否每条路径的黑色相同
if (blackcheck != blacknum)
{
cout << "路径上黑色个数不同" << ' ';
return false;
}
return true;
}
//判断是否有两个连续的红色
Node* parent = root->_parent;
if (root->_col == RED)
{
if (parent && parent->_col == RED)
{
cout << "有连续的红色" << ' ';
return false;
}
}
if (root->_col == BLACK) blacknum++;
return CheckColor(root->_left, blackcheck, blacknum)
&& CheckColor(root->_right, blackcheck, blacknum);
}
private:
Node* _root = nullptr;
};
二.map和set
1.基本实现
map和set虽然功能不同,但在库里都是使用红黑树实现的,接下来对红黑树的代码进行改造。在库里,set和map走的是泛型,也就是map和set可以使用同一份红黑树代码。
对红黑树进行泛化处理,方便之后传参
这里有一个问题:对于data,如果是set那么我们可以直接比较,但如果是map呢?map的T是一个pair,我们是不能直接比较的,为了解决这个问题,我们可以使用仿函数(如果不了解可以看看我的仿函数这篇博客)。
map里返回pair的firist
set为了保持一致,直接返回key
在树里创建一个对象,用该对象的规则进行比较
分别对map和set加入插入操作
2.迭代器
首先需要明确迭代器的功能,就是能够将整棵树进行中序遍历。
我们需要++,*,–,!=等操作。对于++操作,我们需要进行中序遍历。
其他一些小功能就不细说,下面是完整代码
RBTree.h
#pragma once
#include<iostream>
using namespace std;
enum Colour
{
RED,
BLACK
};
template<class T>
struct RBTreeNode
{
RBTreeNode<T>* _left;
RBTreeNode<T>* _right;
RBTreeNode<T>* _parent;
T _data;
Colour _col;
RBTreeNode(const T& data)
:_left(nullptr)
,_right(nullptr)
,_parent(nullptr)
,_data(data)
,_col(RED)
{}
};
template<class T>
struct __TreeIterator
{
typedef RBTreeNode<T> Node;
typedef __TreeIterator<T> Self;
Node* _node;
__TreeIterator(Node* node)
:_node(node)
{}
T& operator*()
{
return _node->_data;
}
T* operator->()
{
return &_node->_data;
}
bool operator!=(const Self& s)
{
return _node != s._node;
}
Self& operator++()
{
if (_node->_right)
{
// 右树的最左节点(最小节点)
Node* subLeft = _node->_right;
while (subLeft->_left)
{
subLeft = subLeft->_left;
}
_node = subLeft;
}
else
{
Node* cur = _node;
Node* parent = cur->_parent;
// 找孩子是父亲左的那个祖先节点,就是下一个要访问的节点
while (parent)
{
if (cur == parent->_left)
{
break;
}
else
{
cur = cur->_parent;
parent = parent->_parent;
}
}
_node = parent;
}
return *this;
}
};
// set->RBTree<K, K, SetKeyOfT> _t;
// map->RBTree<K, pair<K, V>, MapKeyOfT> _t;
template<class K, class T, class KeyOfT>
struct RBTree
{
typedef RBTreeNode<T> Node;
public:
typedef __TreeIterator<T> iterator;
// const_iterator
iterator begin()
{
Node* leftMin = _root;
while (leftMin && leftMin->_left)
{
leftMin = leftMin->_left;
}
return iterator(leftMin);
}
iterator end()
{
return iterator(nullptr);
}
Node* Find(const K& key)
{
Node* cur = _root;
KeyOfT kot;
while (cur)
{
if (kot(cur->_data) < key)
{
cur = cur->_right;
}
else if (kot(cur->_data) > key)
{
cur = cur->_left;
}
else
{
return cur;
}
}
return nullptr;
}
bool Insert(const T& data)
{
if (_root == nullptr)
{
_root = new Node(data);
_root->_col = BLACK;
return true;
}
Node* parent = nullptr;
Node* cur = _root;
KeyOfT kot;
while (cur)
{
if (kot(cur->_data) < kot(data))
{
parent = cur;
cur = cur->_right;
}
else if (kot(cur->_data) > kot(data))
{
parent = cur;
cur = cur->_left;
}
else
{
return false;
}
}
cur = new Node(data);
cur->_col = RED;
if (kot(parent->_data) < kot(data))
{
parent->_right = cur;
}
else
{
parent->_left = cur;
}
cur->_parent = parent;
while (parent && parent->_col == RED)
{
Node* grandfather = parent->_parent;
if (parent == grandfather->_left)
{
Node* uncle = grandfather->_right;
// u存在且为红
if (uncle && uncle->_col == RED)
{
// 变色
parent->_col = uncle->_col = BLACK;
grandfather->_col = RED;
// 继续向上处理
cur = grandfather;
parent = cur->_parent;
}
else // u不存在 或 存在且为黑
{
if (cur == parent->_left)
{
// g
// p
// c
RotateR(grandfather);
parent->_col = BLACK;
grandfather->_col = RED;
}
else
{
// g
// p
// c
RotateL(parent);
RotateR(grandfather);
cur->_col = BLACK;
grandfather->_col = RED;
}
break;
}
}
else // parent == grandfather->_right
{
Node* uncle = grandfather->_left;
// u存在且为红
if (uncle && uncle->_col == RED)
{
// 变色
parent->_col = uncle->_col = BLACK;
grandfather->_col = RED;
// 继续向上处理
cur = grandfather;
parent = cur->_parent;
}
else
{
if (cur == parent->_right)
{
// g
// p
// c
RotateL(grandfather);
grandfather->_col = RED;
parent->_col = BLACK;
}
else
{
// g
// p
// c
RotateR(parent);
RotateL(grandfather);
cur->_col = BLACK;
grandfather->_col = RED;
}
break;
}
}
}
_root->_col = BLACK;
return true;
}
void RotateL(Node* parent)
{
++_rotateCount;
Node* cur = parent->_right;
Node* curleft = cur->_left;
parent->_right = curleft;
if (curleft)
{
curleft->_parent = parent;
}
cur->_left = parent;
Node* ppnode = parent->_parent;
parent->_parent = cur;
if (parent == _root)
{
_root = cur;
cur->_parent = nullptr;
}
else
{
if (ppnode->_left == parent)
{
ppnode->_left = cur;
}
else
{
ppnode->_right = cur;
}
cur->_parent = ppnode;
}
}
void RotateR(Node* parent)
{
++_rotateCount;
Node* cur = parent->_left;
Node* curright = cur->_right;
parent->_left = curright;
if (curright)
curright->_parent = parent;
Node* ppnode = parent->_parent;
cur->_right = parent;
parent->_parent = cur;
if (ppnode == nullptr)
{
_root = cur;
cur->_parent = nullptr;
}
else
{
if (ppnode->_left == parent)
{
ppnode->_left = cur;
}
else
{
ppnode->_right = cur;
}
cur->_parent = ppnode;
}
}
bool CheckColour(Node* root, int blacknum, int benchmark)
{
if (root == nullptr)
{
if (blacknum != benchmark)
return false;
return true;
}
if (root->_col == BLACK)
{
++blacknum;
}
if (root->_col == RED && root->_parent && root->_parent->_col == RED)
{
cout << root->_kv.first << "出现连续红色节点" << endl;
return false;
}
return CheckColour(root->_left, blacknum, benchmark)
&& CheckColour(root->_right, blacknum, benchmark);
}
bool IsBalance()
{
return IsBalance(_root);
}
bool IsBalance(Node* root)
{
if (root == nullptr)
return true;
if (root->_col != BLACK)
{
return false;
}
// 基准值
int benchmark = 0;
Node* cur = _root;
while (cur)
{
if (cur->_col == BLACK)
++benchmark;
cur = cur->_left;
}
return CheckColour(root, 0, benchmark);
}
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;
}
private:
Node* _root = nullptr;
public:
int _rotateCount = 0;
};
Map.h
#include"RBTree.h"
namespace Mine
{
template<class K, class V>
class map
{
struct MapKeyOfT
{
const K& operator()(const pair<K, V>& kv)
{
return kv.first;
}
};
public:
typedef typename RBTree<K, pair<K, V>, MapKeyOfT>::iterator iterator;
iterator begin()
{
return _t.begin();
}
iterator end()
{
return _t.end();
}
V& operator[](const K& key);
bool insert(const pair<K, V>& kv)
{
return _t.Insert(kv);
}
private:
RBTree<K, pair<K, V>, MapKeyOfT> _t;
};
}
Set.h
#include"RBTree.h"
namespace Mine
{
template<class K>
class set
{
struct SetKeyOfT
{
const K& operator()(const K& key)
{
return key;
}
};
public:
typedef typename RBTree<K, K, SetKeyOfT>::iterator iterator;
iterator begin()
{
return _t.begin();
}
iterator end()
{
return _t.end();
}
bool insert(const K& key)
{
return _t.Insert(key);
}
private:
RBTree<K, K, SetKeyOfT> _t;
};
}