红黑树链接入口
底层容器
模拟实现set和map时常用的底层容器是红黑树
。
红黑树是一种自平衡的搜索二叉树,通过对节点进行颜色标记来保持平衡。
在模拟实现set和map时,可以使用红黑树来按照元素的大小自动排序,并且保持插入和删除操作的高效性。set的每个节点只存储一个键值,不需要额外的值;而map每个节点存储的是一个键值对,值与键保持关联。通过红黑树的特性,可以根据快速查找,插入和删除对应的节点元素;
红黑树的改造
#pragma once
#include<vector>
enum Colour
{
RED,
BLACK
};
template<class T>
struct RBTreeNode
{
RBTreeNode<T>* _left;
RBTreeNode<T>* _right;
RBTreeNode<T>* _parent;
Colour _col;
T _data;
RBTreeNode(const T& data)
:_left(nullptr)
, _right(nullptr)
, _parent(nullptr)
, _data(data)
, _col(RED)
{
}
};
//红黑树的迭代器
template<class T,class Ptr,class Ref>
struct RBTreeIterator
{
typedef RBTreeNode<T> Node;
typedef RBTreeIterator<T,Ptr,Ref> Self;
Node* _node;
RBTreeIterator(Node* node)
:_node(node)
{}
Ref operator*()
{
return _node->_data;
}
Ptr operator->()
{
return &_node->_data;
}
Self& operator++()
{
if (_node->_right)
{
Node* subLeft = _node->_right;
while (subLeft->_left)
{
subLeft = subLeft->_left;
}
_node = subLeft;
}
else
{
Node* cur = _node;
Node* parent = cur->_parent;
while (parent&&cur==parent->_right)
{
cur = parent;
parent = parent->_parent;
}
_node = parent;
}
return *this;
}
Self& operator--()
{
if (_node->_left)
{
Node* subRight = _node->_left;
while (subRight->_right)
{
subRight = subRight->_right;
}
_node = subRight;
}
else
{
Node* cur = _node;
Node* parent = cur->_parent;
while (parent && cur == parent->_left)
{
cur = parent;
parent = parent->_parent;
}
_node = parent;
}
return *this;
}
bool operator!=(const Self& s)
{
return _node != s._node;
}
bool operator == (const Self & s)
{
return _node == s._node;
}
};
//set->RBTree<K,K,SetOfT>
//map->RBTree<K,pair<K,V>,MapKeyOfT>
template<class K,class T,class KeyOfT>
class RBTree
{
typedef RBTreeNode<T> Node;
public:
typedef RBTreeIterator<T,T*,T&> iterator;
typedef RBTreeIterator<T, const T*, const T&> const_iterator;
const_iterator begin() const
{
Node* subLeft = _root;
while (subLeft && subLeft->_left)
{
subLeft = subLeft->_left;
}
return const_iterator(subLeft);
}
iterator begin()
{
Node* subLeft = _root;
while (subLeft && subLeft->_left)
{
subLeft = subLeft->_left;
}
return iterator(subLeft);
}
const_iterator end() const
{
return const_iterator(nullptr);
}
iterator end()
{
return iterator(nullptr);
}
iterator Find(const K& key)
{
KeyOfT kot;
Node* cur = _root;
//通过比较确定key节点的位置
while (cur)
{
if (kot(cur->_data) < key)
{
cur = cur->_right;
}
else if (kot(cur->_data) > key)
{
cur = cur->_left;
}
else
{
return iterator(cur);
}
}
//找不到返回最后的end
return end();
}
pair<iterator,bool> Insert(const T& data)
{
if (_root == nullptr)
{
_root = new Node(data);
_root->_col = BLACK;
return make_pair(iterator(_root),true);
}
//确定插入位置
KeyOfT kot;
Node* parent = nullptr;
Node* cur = _root;
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 make_pair(iterator(cur), false);
}
}
//确定cur节点和p节点的位置关系
cur = new Node(data);
//要记住当前节点的位置
Node* newnode = cur;
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;
//情况一
if (uncle && uncle->_col == RED)
{
parent->_col = uncle->_col = BLACK;
grandfather->_col = RED;
//向上处理
cur = grandfather;
parent = cur->_parent;
}
else//情况2
{
if (cur == parent->_left)
{
// g
// p u
// c
RotateR(grandfather);
parent->_col = BLACK;
grandfather->_col = RED;
}
else
{
// g
// p u
// c
RotateL(parent);
RotateR(grandfather);
cur->_col = BLACK;
grandfather->_col = RED;
}
break;//旋转完的子树的根节点必为黑,这时就不用向上调整处理了
}
}
else
{
Node* uncle = grandfather->_left;
// 情况一:叔叔存在且为红
if (uncle && uncle->_col == RED)
{
// 变色
parent->_col = uncle->_col = BLACK;
grandfather->_col = RED;
// 继续往上处理
cur = grandfather;
parent = cur->_parent;
}
else//情况2
{
if (cur == parent->_right)
{
// g
// u p
// c
RotateL(grandfather);
parent->_col = BLACK;
grandfather->_col = RED;
}
else
{
// g
// u p
// c
RotateR(parent);
RotateL(grandfather);
cur->_col = BLACK;
grandfather->_col = RED;
}
break;//旋转完的子树的根节点必为黑,这时就不用向上调整处理了
}
}
}
_root->_col = BLACK;
return make_pair(iterator(newnode), true);
}
void RotateL(Node* parent)
{
Node* subR = parent->_right;
Node* subRL = subR->_left;
parent->_right = subRL;
if (subRL)
subRL->_parent = parent;
subR->_left = parent;
Node* ppnode = parent->_parent;
parent->_parent = subR;
if (parent == _root)
{
_root = subR;
subR->_parent = nullptr;
}
else
{
if (ppnode->_left == parent)
{
ppnode->_left = subR;
}
else
{
ppnode->_right = subR;
}
subR->_parent = ppnode;
}
}
void RotateR(Node* parent)
{
Node* subL = parent->_left;
Node* subLR = subL->_right;
parent->_left = subLR;
if (subLR)
subLR->_parent = parent;
subL->_right = parent;
Node* ppnode = parent->_parent;
parent->_parent = subL;
if (parent == _root)
{
_root = subL;
subL->_parent = nullptr;
}
else
{
if (ppnode->_left == parent)
{
ppnode->_left = subL;
}
else
{
ppnode->_right = subL;
}
subL->_parent = ppnode;
}
}
private:
Node* _root = nullptr;
};
红黑树的迭代器
map和set的模拟实现
Mymap.h
namespace fnc
{
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<const K, V>, MapKeyOfT>::iterator iterator;
typedef typename RBTree<K, pair<const K, V>, MapKeyOfT>::const_iterator const_iterator;
iterator begin()
{
return _t.begin();
}
iterator end()
{
return _t.end();
}
const_iterator begin() const
{
return _t.begin();
}
const_iterator end() const
{
return _t.end();
}
pair<iterator, bool> insert(const pair<K, V>& kv)
{
return _t.Insert(kv);
}
V& operator[](const K& key)
{
pair<iterator, bool> ret = insert(make_pair(key, V()));
return ret.first->second;
}
iterator find(const K& key)
{
return _t.Find(key);
}
private:
RBTree<K, pair<const K, V>, MapKeyOfT> _t;
};
}
Myset.h
namespace fnc
{
template<class K>
class set
{
struct SetKeyOfT
{
const K& operator()(const K& key)
{
return key;
}
};
public:
typedef typename RBTree<K, const K, SetKeyOfT>::iterator iterator;
typedef typename RBTree<K, const K, SetKeyOfT>::const_iterator const_iterator;
iterator begin()
{
return _t.begin();
}
iterator end()
{
return _t.end();
}
pair<iterator,bool> insert(const K& key)
{
return _t.Insert(key);
}
private:
RBTree<K, const K, SetKeyOfT> _t;
};
}
测试
void test_map1()
{
map<int, int> m;
int a[] = { 4, 2, 6, 1, 3, 5, 15, 7, 16, 14 };
for (auto e : a)
{
m.insert(make_pair(e,e));
}
map<int, int>::iterator it = m.begin();
while (it != m.end())
{
it->second += 100;
cout << it->first << "," << it->second << endl;
++it;
}
cout << endl;
}
void test_set1()
{
set<int> s;
int a[] = { 4, 2, 6, 1, 3, 5, 15, 7, 16, 14 };
for (auto e : a)
{
s.insert(e);
}
set<int>::iterator it = s.begin();
while (it != s.end())
{
cout << *it << " ";
++it;
}
cout << endl;
}
operator[]
void test_map2()
{
string arr[] = { "西瓜","草莓","香蕉","苹果","西瓜","草莓","香蕉" ,"西瓜","草莓","西瓜" };
map<string, int> countmap;
for (auto& e : arr)
{
countmap[e]++;
}
for (auto& kv : countmap)
{
cout << kv.first << ":" << kv.second << " ";
}
cout << endl;
}
完善
验证
void test_map3()
{
map<int, int> m;
int a[] = { 4, 2, 6, 1, 3, 5, 15, 7, 16, 14 };
for (auto e : a)
{
m.insert(make_pair(e, e));
}
const map<int, int> m1 = m;
map<int, int>::const_iterator it = m1.begin();
while (it != m1.end())
{
cout << it->first << "," << it->second << endl;
++it;
}
cout << endl;
map<int, int>::iterator it2 = m.find(15);
--it2;
cout << it2->first << "," << it2->second << endl;
}