STL 改造红黑树 模拟封装set和map
改造红黑树
在初次看STL中实现红黑树的源码时有些不理解,然后自己尝试对set以RBTree<K,K>的方式封装红黑树的迭代器;实现过程发现,这样封装复用程度特别低,也特别冗余,因此才能领悟到STL源码实现红黑树复用时的精髓.下文将模拟STL的实现方式改造红黑树和封装map和set.
参考的STL版本为SGI30
适配STL迭代器的红黑树
红黑树数据操作的代码实现是旧版本的,新版本在上一篇博客中有详细分析.
本篇主要特点在迭代器适配上
基本结构
#pragma once
#include<assert.h>
#include<iostream>
using std::cout;
using std::endl;
using std::cin;
using std::pair;
using std::make_pair;
using std::string;
namespace test
{
enum Colour { RED, BLACK };
template<class T> struct RBTreeNode;
template<class T, class Ref, typename Ptr> struct __RBTree_iterator;
template<class K, class T, class keyOfT> class RBTree;
}
RBTreeNode
template<class T> // T为key或pair,T是key或者key-value类型
struct RBTreeNode
{
RBTreeNode* _left;
RBTreeNode* _right;
RBTreeNode* _parent;
T _data; //data是key或pair
Colour _col;
RBTreeNode(const T& data)
: _left(nullptr)
, _right(nullptr)
, _parent(nullptr)
, _data(data)
, _col(RED)
{}
};
__RBTree_iterator
template<class T, class Ref, typename Ptr>
struct __RBTree_iterator
{
typedef RBTreeNode<T> node;
node* _node;
__RBTree_iterator(node* node)
:_node(node)
{}
//首先,<class T, class Ref, class Ptr>这种写法能够提高复用性和灵活性(实现不同类型的迭代器)等,,库里迭代器都这么写
//其次,模板参数中,T用于获取类型,Ref用于返回引用,Ptr用于返回指针
using Self = __RBTree_iterator<T,Ref,Ptr>; //自己--实例化出下面两种迭代器
using iterator = __RBTree_iterator<T,T&,T*>; //普通迭代器
using const_iterator = __RBTree_iterator<T,const T&,const T*>; //const迭代器
__RBTree_iterator(const iterator& it)
:_node(it._node)
{}
//这个构造函数的作用,
//a.当迭代器被实例化成iterator时,他就是拷贝构造函数. __RBTree_iterator<T,T&,T*>
//b.当迭代器被实例化成const_iterator时,他是支持隐式类型转换的带参构造函数. __RBTree_iterator<T,const T&,const T*>
//这样实现的目的
// 能够复用普通迭代器,可以通过类型转换后直接实现出const迭代器
//Ref为 T& 或 const T&, Ptr为 T* 或 const T*
//typedef __RBTree_iterator<T, Ref, Ptr> Self;
Ref operator*()
{
return _node->_data;
}
Ptr operator->()
{
return &(_node->_data);
}
bool operator!=(const Self& x)
{
return _node != x._node;
}
//前置++
Self& operator++() {
//此版本实现迭代器不需要判空,为空说明遍历结束,要么是用户错误使用
Node* cur = _node;
//1. 有右子树
if (cur->_right) {
//找右子树的最小结点
Node* rightMin = cur->_right;
while (rightMin->_left) {
rightMin = rightMin->_left;
}
_node = rightMin;
}
//2. 没有右子树
else {
////1.没有父亲,说明是根
//Node* parent = cur->_parent;
//if (parent == nullptr) {
// _node == nullptr;
//}
////2.且我是父的左子树,说明父亲是下一个正序值
//else if (parent->_left == cur) {
// _node = parent;
//}
////3.或我是父亲的右子树,说明走完了当前最小分支祖先这棵树.迭代往上
//else if (parent->_right == cur) {
// while (parent && cur != parent->_left) {
// cur = parent;
// parent = parent->_parent;
// }
// _node = parent;
//}
//else {
// asssert(false);
//}
//上面3种情况可以合并成一种情况:找最近的不是右孩子的祖父
Node* parent = cur->_parent;
while (parent && cur != parent->_left) {
cur = parent;
parent = parent->_parent;
}
_node = parent;
}
return *this;
}
//后置++
Self operator++(int) {
Self tmp(_node);
operator++();
return tmp;
}
Self& operator--() {
//将++反过来就是--
Node* cur = _node;
//左子树存在,就找最大
if (cur->_left) {
Node* leftMax = cur->_left;
while (leftMax->_right) {
leftMax = leftMax->_right;
}
_node = leftMax;
}
//2. 没有左子树
else {
Node* parent = cur->_parent;
while (parent && cur != parent->_right) {
cur = parent;
parent = parent->_parent;
}
_node = parent;
}
return *this;
}
Self operator--(int) {
Self tmp(_node);
operator--();
return tmp;
}
};
RBTree
//参数K用在find,erase等,虽然K也可以被T取代了,但没必要,K更快
template<class K, class T, class keyOfT> //库中还有1个compare，先不写了
class RBTree
{
public:
typedef RBTreeNode<T> node; //T是key或pair
public:
typedef __RBTree_iterator<T, T&, T*> iterator;
typedef __RBTree_iterator<T, const T&, const T*> const_iterator;
iterator begin()
{
node* cur = _root;
while (cur && cur->_left)//不能走到空
{
cur = cur->_left;
}
return iterator(cur);//返回中序的第一个结点,最左结点
}
iterator end() //end是最一个位置的下一个
{
return iterator(nullptr);//暂时可以这么写
}
const_iterator begin()const
{
node* cur = _root;
while (cur && cur->_left)
{
cur = cur->_left;
}
return iterator(cur);
}
const_iterator end() const
{
return iterator(nullptr);
}
private:
node* _root = nullptr;
public:
node* find(const K& key)
{
keyOfT kot;//kot是个仿函数,根据不同参数返回不同的参数对象
node* cur = _root;
while (cur)
{
if (key < kot(cur->_data)) // -------------------------------------------- 只需要重载一个 '<' 或 '>' 就可以比较大小
{
cur = cur->_left;
}
else if (kot(cur->_data) < key) // --------------------------------------------只需要重载一个 '<' 或 '>' 就可以比较大小
{
cur = cur->_right;
}
else
{
return cur;
}
}
return nullptr;
}
pair<iterator, bool> insert(const T& data)
{
if (!_root)
{
_root = new node(data);
_root->_col = BLACK;
return std::make_pair(iterator(_root), true);
}
keyOfT kot;
node* cur = _root;
node* parent = nullptr;
while (cur)
{
if (kot(cur->_data) < kot(data) ) // --------------------------------------------只需要重载一个 '<' 或 '>' 就可以比较大小
{
parent = cur;
cur = cur->_right;
}
else if (kot(data) < kot(cur->_data)) // --------------------------------------------只需要重载一个 '<' 或 '>' 就可以比较大小
{
parent = cur;
cur = cur->_left;
}
else
{
return std::make_pair(iterator(cur), false);
}
}
cur = new node(data);
if ( kot(parent->_data) < kot(data)) // --------------------------------------------
{
parent->_right = cur;
}
else
{
parent->_left = cur;
}
cur->_parent = parent;
//调整/旋转
node* newnode = cur;//调整过程cur会发生变化,将cur结点记住 -- 记住原来key的位置
while (parent && parent->_col == RED)
{
node* g = parent->_parent;
if (parent == g->_right)
{
node* u = g->_left;
if (u && u->_col == RED)
{
g->_col = RED;
parent->_col = BLACK;
u->_col = BLACK;
cur = g;
parent = cur->_parent;
}
else
{
if (cur == parent->_right)
{
RotateL(g);
parent->_col = BLACK;
g->_col = RED;
}
else
{
RotateR(parent);
RotateL(g);
g->_col = RED;
cur->_col = BLACK;
}
break;
}
}
else
{
node* u = g->_right;
if (u && u->_col == RED)
{
g->_col = RED;
parent->_col = BLACK;
u->_col = BLACK;
cur = g;
parent = cur->_parent;
}
else
{
if (cur == parent->_left)
{
RotateR(g);
parent->_col = BLACK;
g->_col = RED;
}
else
{
RotateL(parent);
RotateR(g);
g->_col = RED;
cur->_col = BLACK;
}
break;
}
}
}
_root->_col = BLACK;
return std::make_pair(iterator(newnode), true);
}
public:
void InOrderTraversal()
{
_InOrderTraversal(_root);
}
bool isBalanceTree()
{
//需要判断3个规则
//1.根为黑
if (_root && _root->_col == RED)
{
cout << "错误:根是红色" << endl;
return false;
}
//2.不能有连续得红
//3.黑同
int benchmark = 0;
node* cur = _root;
while (cur)
{
if (cur->_col == BLACK)
{
++benchmark;
}
cur = cur->_left;
}
return _check(_root, 0, benchmark);
}
int Height()
{
return _Height(_root);
}
~RBTree()
{
Destroy(_root);
}
private:
void Destroy(node*& root)
{
if (!root)
{
return;
}
Destroy(root->_left);
Destroy(root->_right);
delete root;
root = nullptr;
}
bool _check(node* root, int blackNum, int benchmark)
{
keyOfT kot;
if (!root) //
{
if (blackNum != benchmark)
{
cout << "错误:存在不同路径的黑色结点数量不相同" << endl;
return false;
}
return true;
}
if (root->_col == BLACK)
{
++blackNum;
}
if (root->_col == RED && root->_parent->_col == RED)
{
cout << kot(root->_data) << " 错误,与父节点同时为红色"; // --------------------------------------------
return false;
}
return _check(root->_left, blackNum, benchmark) && _check(root->_right, blackNum, benchmark);
}
int _Height(node* root)
{
if (!root)
{
return 0;
}
int leftH = _Height(root->_left);
int rightH = _Height(root->_right);
return leftH > rightH ? leftH + 1 : rightH + 1;
}
void _InOrderTraversal(node* root)
{
keyOfT kot;
if (root == nullptr)
{
return;
}
_InOrderTraversal(root->_left);
cout << kot(root->_data) << " "; // --------------------------------------------
_InOrderTraversal(root->_right);
}
void RotateL(node* parent)
{
node* subR = parent->_right;
node* subRL = subR->_left;
parent->_right = subRL;
if (subRL)
{
subRL->_parent = parent;
}
node* pparent = parent->_parent;
subR->_left = parent;
parent->_parent = subR;
if (!pparent)
{
_root = subR;
_root->_parent = nullptr;
}
else
{
if (pparent->_left == parent)
{
pparent->_left = subR;
}
else
{
pparent->_right = subR;
}
subR->_parent = pparent;
}
}
void RotateR(node* parent)
{
node* subL = parent->_left;
node* subLR = subL->_right;
parent->_left = subLR;
if (subLR)
{
subLR->_parent = parent;
}
node* pparent = parent->_parent;
subL->_right = parent;
parent->_parent = subL;
if (parent == _root)
{
_root = subL;
_root->_parent = nullptr;
}
else
{
if (pparent->_left == parent)
{
pparent->_left = subL;
}
else
{
pparent->_right = subL;
}
subL->_parent = pparent;
}
}
};
完整代码
#pragma once
#include<assert.h>
#include<iostream>
using std::cout;
using std::endl;
using std::cin;
using std::pair;
using std::make_pair;
using std::string;
namespace test
{
//与库中的RBT差异
/**
*
* 库中还有结点数量 count
*
* 库中RBT是带头结点哨兵卫的,头结点的左是中序第一个(最小结点),右节点是中序的最后一个(最大结点),
* 哨兵卫的parent指向根节点,根节点的parent指向哨兵卫
*
* 库中的begin直接取head的left -- 函数:leftmost() //最左结点
* 库中的end 是head的right -- 不是rightmost,rightmost是最右结点,end是最右结点的下一个
* 库中的end 需要判断一下,防止只有左子树的歪脖子树时,end == head->right,死循环
*
* 和库的区别就是end,库的end能走回到head,我的不能,只能走到空就没了d
*
*/
enum Colour { RED, BLACK };
template<class T> //T是什么,为什么只传T? T为key或pair,T是key或者key-value类型
struct RBTreeNode
{
RBTreeNode* _left;
RBTreeNode* _right;
RBTreeNode* _parent;
T _data; //data是key或pair
Colour _col;
RBTreeNode(const T& data)
: _left(nullptr)
, _right(nullptr)
, _parent(nullptr)
, _data(data)
, _col(RED)
{}
};
//const_iterator<T,const T&,const T*>
//iterator<T, T&, T*>
template<class T, class Ref, typename Ptr>
struct __RBTree_iterator
{
typedef RBTreeNode<T> node;
node* _node;
__RBTree_iterator(node* node)
:_node(node)
{}
//首先,<class T, class Ref, class Ptr>这种写法能够提高复用性和灵活性(实现不同类型的迭代器)等,,库里迭代器都这么写
//其次,模板参数中,T用于获取类型,Ref用于返回引用,Ptr用于返回指针
using Self = __RBTree_iterator<T,Ref,Ptr>; //自己--实例化出下面两种迭代器
using iterator = __RBTree_iterator<T,T&,T*>; //普通迭代器
using const_iterator = __RBTree_iterator<T,const T&,const T*>; //const迭代器
__RBTree_iterator(const iterator& it)
:_node(it._node)
{}
//这个构造函数的作用,
//a.当迭代器被实例化成iterator时,他就是拷贝构造函数. __RBTree_iterator<T,T&,T*>
//b.当迭代器被实例化成const_iterator时,他是支持隐式类型转换的带参构造函数. __RBTree_iterator<T,const T&,const T*>
//这样实现的目的
// 能够复用普通迭代器,可以通过类型转换后直接实现出const迭代器
//Ref为 T& 或 const T&, Ptr为 T* 或 const T*
//typedef __RBTree_iterator<T, Ref, Ptr> Self;
Ref operator*()
{
return _node->_data;
}
Ptr operator->()
{
return &(_node->_data);
}
bool operator!=(const Self& x)
{
return _node != x._node;
}
//前置++
Self& operator++() {
//此版本实现迭代器不需要判空,为空说明遍历结束,要么是用户错误使用
Node* cur = _node;
//1. 有右子树
if (cur->_right) {
//找右子树的最小结点
Node* rightMin = cur->_right;
while (rightMin->_left) {
rightMin = rightMin->_left;
}
_node = rightMin;
}
//2. 没有右子树
else {
////1.没有父亲,说明是根
//Node* parent = cur->_parent;
//if (parent == nullptr) {
// _node == nullptr;
//}
////2.且我是父的左子树,说明父亲是下一个正序值
//else if (parent->_left == cur) {
// _node = parent;
//}
////3.或我是父亲的右子树,说明走完了当前最小分支祖先这棵树.迭代往上
//else if (parent->_right == cur) {
// while (parent && cur != parent->_left) {
// cur = parent;
// parent = parent->_parent;
// }
// _node = parent;
//}
//else {
// asssert(false);
//}
//上面3种情况可以合并成一种情况:找最近的不是右孩子的祖父
Node* parent = cur->_parent;
while (parent && cur != parent->_left) {
cur = parent;
parent = parent->_parent;
}
_node = parent;
}
return *this;
}
//后置++
Self operator++(int) {
Self tmp(_node);
operator++();
return tmp;
}
Self& operator--() {
//将++反过来就是--
Node* cur = _node;
//左子树存在,就找最大
if (cur->_left) {
Node* leftMax = cur->_left;
while (leftMax->_right) {
leftMax = leftMax->_right;
}
_node = leftMax;
}
//2. 没有左子树
else {
Node* parent = cur->_parent;
while (parent && cur != parent->_right) {
cur = parent;
parent = parent->_parent;
}
_node = parent;
}
return *this;
}
Self operator--(int) {
Self tmp(_node);
operator--();
return tmp;
}
};
//参数K用在find,erase等,虽然K也可以被T取代了,但没必要,K更快
template<class K, class T, class keyOfT> //库中还有1个compare，先不写了
class RBTree
{
public:
typedef RBTreeNode<T> node; //T是key或pair
public:
typedef __RBTree_iterator<T, T&, T*> iterator;
typedef __RBTree_iterator<T, const T&, const T*> const_iterator;
iterator begin()
{
node* cur = _root;
while (cur && cur->_left)//不能走到空
{
cur = cur->_left;
}
return iterator(cur);//返回中序的第一个结点,最左结点
}
iterator end() //end是最一个位置的下一个
{
return iterator(nullptr);//暂时可以这么写
}
const_iterator begin()const
{
node* cur = _root;
while (cur && cur->_left)
{
cur = cur->_left;
}
return iterator(cur);
}
const_iterator end() const
{
return iterator(nullptr);
}
private:
node* _root = nullptr;
public:
node* find(const K& key)
{
keyOfT kot;//kot是个仿函数,根据不同参数返回不同的参数对象
node* cur = _root;
while (cur)
{
if (key < kot(cur->_data)) // -------------------------------------------- 只需要重载一个 '<' 或 '>' 就可以比较大小
{
cur = cur->_left;
}
else if (kot(cur->_data) < key) // --------------------------------------------只需要重载一个 '<' 或 '>' 就可以比较大小
{
cur = cur->_right;
}
else
{
return cur;
}
}
return nullptr;
}
pair<iterator, bool> insert(const T& data)
{
if (!_root)
{
_root = new node(data);
_root->_col = BLACK;
return std::make_pair(iterator(_root), true);
}
keyOfT kot;
node* cur = _root;
node* parent = nullptr;
while (cur)
{
if (kot(cur->_data) < kot(data) ) // --------------------------------------------只需要重载一个 '<' 或 '>' 就可以比较大小
{
parent = cur;
cur = cur->_right;
}
else if (kot(data) < kot(cur->_data)) // --------------------------------------------只需要重载一个 '<' 或 '>' 就可以比较大小
{
parent = cur;
cur = cur->_left;
}
else
{
return std::make_pair(iterator(cur), false);
}
}
cur = new node(data);
if ( kot(parent->_data) < kot(data)) // --------------------------------------------
{
parent->_right = cur;
}
else
{
parent->_left = cur;
}
cur->_parent = parent;
//调整/旋转
node* newnode = cur;//调整过程cur会发生变化,将cur结点记住 -- 记住原来key的位置
while (parent && parent->_col == RED)
{
node* g = parent->_parent;
if (parent == g->_right)
{
node* u = g->_left;
if (u && u->_col == RED)
{
g->_col = RED;
parent->_col = BLACK;
u->_col = BLACK;
cur = g;
parent = cur->_parent;
}
else
{
if (cur == parent->_right)
{
RotateL(g);
parent->_col = BLACK;
g->_col = RED;
}
else
{
RotateR(parent);
RotateL(g);
g->_col = RED;
cur->_col = BLACK;
}
break;
}
}
else
{
node* u = g->_right;
if (u && u->_col == RED)
{
g->_col = RED;
parent->_col = BLACK;
u->_col = BLACK;
cur = g;
parent = cur->_parent;
}
else
{
if (cur == parent->_left)
{
RotateR(g);
parent->_col = BLACK;
g->_col = RED;
}
else
{
RotateL(parent);
RotateR(g);
g->_col = RED;
cur->_col = BLACK;
}
break;
}
}
}
_root->_col = BLACK;
return std::make_pair(iterator(newnode), true);
}
public:
void InOrderTraversal()
{
_InOrderTraversal(_root);
}
bool isBalanceTree()
{
//需要判断3个规则
//1.根为黑
if (_root && _root->_col == RED)
{
cout << "错误:根是红色" << endl;
return false;
}
//2.不能有连续得红
//3.黑同
int benchmark = 0;
node* cur = _root;
while (cur)
{
if (cur->_col == BLACK)
{
++benchmark;
}
cur = cur->_left;
}
return _check(_root, 0, benchmark);
}
int Height()
{
return _Height(_root);
}
~RBTree()
{
Destroy(_root);
}
private:
void Destroy(node*& root)
{
if (!root)
{
return;
}
Destroy(root->_left);
Destroy(root->_right);
delete root;
root = nullptr;
}
bool _check(node* root, int blackNum, int benchmark)
{
keyOfT kot;
if (!root) //
{
if (blackNum != benchmark)
{
cout << "错误:存在不同路径的黑色结点数量不相同" << endl;
return false;
}
return true;
}
if (root->_col == BLACK)
{
++blackNum;
}
if (root->_col == RED && root->_parent->_col == RED)
{
cout << kot(root->_data) << " 错误,与父节点同时为红色"; // --------------------------------------------
return false;
}
return _check(root->_left, blackNum, benchmark) && _check(root->_right, blackNum, benchmark);
}
int _Height(node* root)
{
if (!root)
{
return 0;
}
int leftH = _Height(root->_left);
int rightH = _Height(root->_right);
return leftH > rightH ? leftH + 1 : rightH + 1;
}
void _InOrderTraversal(node* root)
{
keyOfT kot;
if (root == nullptr)
{
return;
}
_InOrderTraversal(root->_left);
cout << kot(root->_data) << " "; // --------------------------------------------
_InOrderTraversal(root->_right);
}
void RotateL(node* parent)
{
node* subR = parent->_right;
node* subRL = subR->_left;
parent->_right = subRL;
if (subRL)
{
subRL->_parent = parent;
}
node* pparent = parent->_parent;
subR->_left = parent;
parent->_parent = subR;
if (!pparent)
{
_root = subR;
_root->_parent = nullptr;
}
else
{
if (pparent->_left == parent)
{
pparent->_left = subR;
}
else
{
pparent->_right = subR;
}
subR->_parent = pparent;
}
}
void RotateR(node* parent)
{
node* subL = parent->_left;
node* subLR = subL->_right;
parent->_left = subLR;
if (subLR)
{
subLR->_parent = parent;
}
node* pparent = parent->_parent;
subL->_right = parent;
parent->_parent = subL;
if (parent == _root)
{
_root = subL;
_root->_parent = nullptr;
}
else
{
if (pparent->_left == parent)
{
pparent->_left = subL;
}
else
{
pparent->_right = subL;
}
subL->_parent = pparent;
}
}
};
}
封装的set
红黑树改造完成后,封装set和map就比较简单了,基本上都是套用红黑树的功能,特别方便,这也体会到了实现STL的大佬们的厉害.
#pragma once
#include"RBT.hpp"
namespace test
{
template<class K>
class set
{
private:
struct setKeyOfT//取出RBT的类型T中的key
{
const K& operator()(const K& key)
{
return key;
}
};
private:
RBTree< K, K, setKeyOfT>_t;
public:
//使用类域的要加typename,以防和静态变量冲突
typedef typename RBTree<K, K, setKeyOfT>::const_iterator iterator; //普通迭代器
typedef typename RBTree<K, K, setKeyOfT>::const_iterator const_iterator; //const迭代器
iterator begin()
{
return _t.begin(); //begin是普通迭代器,返回值是const,发生隐式类型转换(单参数)
//如果有相应的构造函数,则支持隐式类型转换 ,但此时迭代器没有参数为迭代器的构造函数,需要添加
}
iterator end()
{
return _t.end();
}
const_iterator begin()const
{
return _t.begin();
}
const_iterator end()const
{
return _t.end();
}
public:
pair<iterator, bool> insert(const K& key)
{
return _t.insert(key);
}
};
void test_mySet1()
{
test::set<int> s;
s.insert(2);
s.insert(1);
s.insert(3);
set<int>::iterator it = s.begin();
//while (it!=s.end())
//{
// cout << *it << " ";
// ++it;
//}
for (auto& e : s)
{
cout << e << " ";
}
cout << *++it << " ";
cout << *--it << " ";
cout << endl;
//*it = 1;////不允许赋值,表达式必须是可以修改的左值 .不能给常量赋值
}
}
封装的map
#pragma once
#include"RBT.hpp"
namespace test
{
template<class K,class V>
class map
{
private:
struct mapKeyOfT
{
const K& operator()(const pair<const K,V>& kv)
{
return kv.first;
}
};
private:
RBTree<K, pair<const K, V>, mapKeyOfT> _t;
public:
typedef typename RBTree<K, pair<const K,V>, mapKeyOfT>::iterator iterator;
iterator begin()
{
return _t.begin();
}
iterator end()
{
return _t.end();
}
public:
pair<iterator,bool> insert(const pair<const 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;
}
};
void test_myMap1()
{
test::map<int, int> m;
m.insert(std::make_pair(1, 1));
m.insert(std::make_pair(3, 3));
m.insert(std::make_pair(2, 2));
test::map<int,int>::iterator it = m.begin();
//while (it != m.end())
//{
// cout << it->first << " ";
// ++it;
//}
for (auto e : m)
{
cout << e.first << " ";
}
cout << (++it)->first << " ";
cout << (--it)->first << " ";
cout << endl;
//it->second = 1; //可以赋值
//it->first = 1;//不允许赋值,表达式必须是可以修改的左值 .不能给常量赋值
}
void test_myMap2()
{
//map的使用
map<std::string, std::string> dict;
dict.insert(std::pair<std::string, std::string>("sort", "排序")); //匿名对象插入
dict.insert(std::make_pair("string", "字符串")); //pair封装插入
dict.insert(std::make_pair("count", "计数"));
dict.insert(std::make_pair("count", "(计数)")); //插入失败的
auto it = dict.begin();
while (it != dict.end())
{
cout << it->first << ":" << it->second << endl;
++it;
}
}
void test_myMap3()
{
std::string arr[] = { "苹果", "西瓜", "苹果", "西瓜", "苹果", "苹果", "西瓜","苹果", "香蕉", "苹果", "香蕉" };
map<std::string, int> countMap;
/*for (auto e : arr)
{
auto ret = countMap.find(x);
if (ret==countMap.end())
{
countMap.insert(std::pair<string, int>(x, 1));
}
else
{
++ret->second;
}
}*/
for (auto& e : arr)
{
++countMap[e];
}
for (auto& s : countMap)
{
cout << s.first << ":" << s.second << endl;
}
}
}
本文来自博客园，作者：HJfjfK，原文链接：https://www.cnblogs.com/DSCL-ing/p/18390555
