C++进阶--mep和set的模拟实现

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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endreturn 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//  cRotateR(grandfather);parent->_col = BLACK;grandfather->_col = RED;}else{//      g//    p    u//      cRotateL(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//           cRotateL(grandfather);parent->_col = BLACK;grandfather->_col = RED;}else{//      g//    u    p//        cRotateR(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;}

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