[数据结构与算法] 菱形继承，STL

开发: C++知识库 Java知识库 JavaScript Python PHP知识库人工智能区块链大数据移动开发嵌入式开发工具数据结构与算法开发测试游戏开发网络协议系统运维
教程: HTML教程 CSS教程 JavaScript教程 Go语言教程 JQuery教程 VUE教程 VUE3教程 Bootstrap教程 SQL数据库教程 C语言教程 C++教程 Java教程 Python教程 Python3教程 C#教程
数码: 电脑笔记本显卡显示器固态硬盘硬盘耳机手机 iphone vivo oppo 小米华为单反装机图拉丁

-> 数据结构与算法 -> 菱形继承，STL -> 正文阅读

[数据结构与算法]菱形继承，STL

文章目录

C++的4个子集

C子集
class子集
STL
template模板
//函数重载参数的类型或者个数不同,在C11里面也可以根据你的作之和右值来判断
void fun(int& a)//左值引用
{
	cout << "fun(int & a)" << endl;
}
void fun(const int& a)//万能引用不管你是左值还是右值
{
	cout << "fun(const int &a)" << endl;
}
void fun(int&& a)//右值引用
{
	cout << "fun(int && a)" << endl;
}
int main()
{
	int a = 10;
	const int b = 20;
	const int& x = b;
	const int& y = 20;
	fun(x);
	fun(y);
	fun(10);
	return 0;
}

在这里插入图片描述
void fun(const int& a)//常引用不管你是左值还是右值都以引用

//函数重载参数的类型或者个数不同,在C11里面也可以根据你的作之和右值来判断
void fun(int& a)//左值引用
{
	cout << "fun(int & a)" << endl;
}
void fun(const int& a)//万能引用不管你是左值还是右值
{
	cout << "fun(const int &a)" << endl;
}
//void fun(int&& a)//右值引用
//{
//	cout << "fun(int && a)" << endl;
//}
int main()
{
	int a = 10;
	const int b = 20;
	const int& x = b;
	const int& y = 20;
	fun(x);
	fun(y);
	fun(10);//首先找右值引用，其次是找常引用函数
	return 0;
}

在这里插入图片描述

void fun(int& a)//左值引用
{
	cout << "fun(int & a)" << endl;
}
void fun(const int& a)//万能引用不管你是左值还是右值
{
	cout << "fun(const int &a)" << endl;
}
void fun(int&& a)//右值引用
{
	cout << "fun(int && a)" << endl;
}
template<class T>
void fac(T&& a)//右值一旦拥有名字将变为左值
{
	fun(a);
}
int main()
{
	int a = 10;
	const int b = 20;
	fac(a);
	fac(b);
	fac(20);
	return 0;
}

在这里插入图片描述

完美转发 std::forward(a)

系统为了避免上述的右值引用的情况产生了新的概念完美转发

void fun(int& a)//左值引用
{
	cout << "fun(int & a)" << endl;
}
void fun(const int& a)//万能引用不管你是左值还是右值
{
	cout << "fun(const int &a)" << endl;
}
void fun(int&& a)//右值引用
{
	cout << "fun(int && a)" << endl;
}
template<class T>
void fac(T&& a)//右值一旦拥有名字将变为左值
{
	//fun(a);
	fun(std::forward<T>(a));
}
int main()
{
	int a = 10;
	const int b = 20;
	fac(a);
	fac(b);
	fac(20);
	return 0;
}

在这里插入图片描述

template<class T>
class Object
{
	T value;
public:
	Object(T x = T()) :value(x) {}
	static int num;
};
template<class T>
int Object<T>::num = 0;
class Base :public Object<int>
{
public: Base() { num += 1; }
	  void Print()const { cout << "Base" << num<<endl; }
};
class Test :public Object<int>
{
public:
	Test() { num += 1; }
	void Print()const { cout << "Test" << num << endl; }
};
int main()
{
	Base b1, b2;
	Test t1, t2;
	b1.Print();
	t1.Print();
	return 0;
}

在这里插入图片描述

template<class T>
class Object
{
	T value;
public:
	Object(T x = T()) :value(x) {}
	static int num;
};
template<class T>
int Object<T>::num = 0;
class Base :public Object<int>
{
public: Base() { num += 1; }
	  void Print()const { cout << "Base" << num<<endl; }
};
class Test :public Object<double>
{
public:
	Test() { num += 1; }
	void Print()const { cout << "Test" << num << endl; }
};
int main()
{
	Base b1, b2;
	Test t1, t2;
	b1.Print();
	t1.Print();
	return 0;
}

在这里插入图片描述

菱形继承

数据冗余导致的不一致性

class Person
{
private:
	string p_id;
	string p_name;
	string p_sex;
	int p_age;
public:
	Person(const string& id, const string& name, const string& sex, int age)
		:p_id(id), p_name(name), p_sex(sex), p_age(age)
	{}
	void print()const
	{
		cout << "id:   " << p_id << endl;
		cout << "name: " << p_name << endl;
		cout << "sex:  " << p_sex << endl;
		cout << "age:  " << p_age << endl;
	}
};
class Student :public Person
{
private:
	string s_id;
public:
	Student(const string& id, const string& name, const string& sex, int age, const string& d)
		:Person(id, name, "男", age), s_id(d)
	{}
};
class Staff :public Person
{
private:
	string s_id;
public:
	Staff(const string& id, const string& name, const string& sex, int age, const string& d)
		:Person(id, name, "女", age), s_id(d)
	{}
};
class Stud_Staff :public Student, public Staff
{
private:
public:
	Stud_Staff(const string& id, const string& name, int age, const string& dd, const string ss)
		:Student(id,name,"男",age,ss),Staff(id,name,"nv",age,dd)
	{

	}
};
int main()
{

	Stud_Staff ss("610431199900000000", "王伟", 23, "20200", "303030");
	ss.Student::print();
	ss.Staff::print();
	Student s1 = ss;
	Staff s2 = ss;
	//Person p = ss;erro因为此类里面有两个人//数据冗余导致的不一致性
	return 0;
}

在这里插入图片描述

虚继承

class Person
{
private:
	string p_id;
	string p_name;
	string p_sex;
	int p_age;
public:
	Person(const string& id, const string& name, const string& sex, int age)
		:p_id(id), p_name(name), p_sex(sex), p_age(age)
	{}
	void print()const
	{
		cout << "id:   " << p_id << endl;
		cout << "name: " << p_name << endl;
		cout << "sex:  " << p_sex << endl;
		cout << "age:  " << p_age << endl;
	}
};
class Student : virtual public Person
{
private:
	string s_id;
public:
	Student(const string& id, const string& name, const string& sex, int age, const string& d)
		:Person(id, name, "男", age), s_id(d)
	{}
};
class Staff :virtual public Person
{
private:
	string s_id;
public:
	Staff(const string& id, const string& name, const string& sex, int age, const string& d)
		:Person(id, name, "女", age), s_id(d)
	{}
};
class Stud_Staff :public Student, public Staff
{
private:
	int num = 10;
public:
	Stud_Staff(const string& id, const string& name, int age, const string& dd, const string ss)
		:Student(id,name,"男",age,ss),Staff(id,name,"女",age,dd)
	,Person("61010","yhping","男",23)
	{
	}
};
int main()
{

	Stud_Staff ss("610431199900000000", "王伟", 23, "20200", "303030");
	ss.Student::print();
	ss.Staff::print();
	Student s1 = ss;
	Staff s2 = ss;
	Person p = ss;
	return 0;
}

在这里插入图片描述

class Object
{
	int value;
public:
	Object(int x = 10) :value(x) {}
 };
class Base :virtual public Object
{
	int num;
public:
	Base(int x = 0) :num(x), Object(x + 10) {}
};
class Test :virtual public Object
{
	int sum;
public:
	Test(int x = 0) :sum(x), Object(x + 10) {}
};
class Det :public Base, public Test
{
private:
	int total;
public:
	Det(int x = 0) :total(x), Base(x + 10), Test(x + 20), Object(x + 100) {}
};
int main()
{
	Det d(0);
	return 0;
}

在这里插入图片描述

菱形继承的多继承

class Object
{
	int value;
public:
	Object(int x = 10) :value(x) {}
	virtual void fun() { cout << "Object" << endl; }
	virtual void add() { cout << "Object::add" << endl; }
 };
class Base :public Object
{
	int num;
public:
	Base(int x = 0) :num(x), Object(x + 10) {}
	virtual void fun() { cout << "Base" << endl; }
};
class Test : public Object
{
	int sum;
public:
	Test(int x = 0) :sum(x), Object(x + 10) {}
	virtual void fun() { cout << "Test" << endl; }
	 void add() { cout << "Test::add" << endl; }
};
class Det :public Base, public Test
{
private:
	int total;
public:
	Det(int x = 0) :total(x), Base(x + 10), Test(x + 20) {}
	 void fun() { cout << "Det" << endl; }
	void add() { cout << "Det::add" << endl; }
};
int main()
{
	Det d(0);
	//Object* op = &d;erro因为d里面Base和Test都有Object
	Object* opa = (Base*)&d;
	Object* opb = (Test*)&d;//opa和opb 是不同的地址
	opa->add();
	opa->fun();

	opb->add();
	opb->fun();
	return 0;
}

在这里插入图片描述

虚继承的多继承

class Object
{
	int value;
public:
	Object(int x = 10) :value(x) {}
	virtual void fun() { cout << "Object" << endl; }
	virtual void add() { cout << "Object::add" << endl; }
 };
class Base :virtual public Object
{
	int num;
public:
	Base(int x = 0) :num(x), Object(x + 10) {}
	virtual void fun() { cout << "Base" << endl; }
};
class Test : virtual public Object
{
	int sum;
public:
	Test(int x = 0) : sum(x), Object(x + 10) {}
	virtual void fun() { cout << "Test" << endl; }
	 void add() { cout << "Test::add" << endl; }
};
class Det :public Base, public Test
{
private:
	int total;
public:
	Det(int x = 0) :total(x), Base(x + 10), Test(x + 20), Object(x + 100) {}
	 void fun() { cout << "Det" << endl; }
	void add() { cout << "Det::add" << endl; }
};
int main()
{
	Det d(0);
	Object* opa = &d;
	Object* opb = &d;//opa和opb 是不同的地址
	opa->add();
	opa->fun();

	opb->add();
	opb->fun();
	return 0;
}

在这里插入图片描述

STL

在这里插入图片描述

STL问的最多的就是配置器和迭代器的失效问题
在这里插入图片描述

字符串库

#include<string>//c++里面的字符串类型
#include<string.h>//C库里面的字符串函数库
#include<cstring>//C库里面的字符串函数库
int main()
{
	string s1 = "yhpingll";
	string s2("yhpingll");
	//string::value_type p;
	string::value_type v;//char v
	string::pointer p = &v;
	string::reference x = v;
	//char&x=v;
	string::const_reference y = v;
	//char const&y=v;

	cout << typeid(p).name() << endl;

}

int main()
{
	string s1 = "abcdefgh";
	string::iterator it = s1.begin();
	for (;it != s1.end(); ++it)
	{
		cout << *it;
	}
	cout << endl;
	string::reverse_iterator rt;
	for (rt = s1.rbegin(); rt != s1.rend(); ++rt)
	{
		cout << *rt;
	}
	cout << endl;
	for (auto& x : s1)
	{
		cout << x;
	}
	cout << endl;
	return 0;
}

在这里插入图片描述

int main()
{
	string s1("yhping");
	string s2("hello");
	cout << s1 << endl;
	cout << s2 << endl;
	s1 = s2;
	cout << s1 << endl;//底层已经对输出流进行了重载
	cout << s2 << endl;
}

在这里插入图片描述

int main()
{
	string s1("yhping");
	string s2("hello");
	cout << s1 << endl;
	cout << s2 << endl;
	s1 = std::move(s2);
	cout << s1 << endl;//底层已经对输出流进行了重载
	cout << s2 << endl;
}

在这里插入图片描述

#include<string>//c++里面的字符串类型
int main()
{
	string s1("yhping");
	cout << "size: " << s1.size() << endl;
	cout << "capacity: " << s1.capacity() << endl;
	s1 += "hellohelloniahoanihaoa";
	cout << "size: " << s1.size() << endl;
	cout << "capacity: " << s1.capacity() << endl;
	return 0;
}

在这里插入图片描述

int main()
{
	string s1("yhping");
	int n = s1.size();
	for (int i = 0; i < n; ++i)
	{//下标访问
		cout << s1[i] << " ";
	}
	cout << endl;
	//在某些STL库里面[]访问并不检查是否越界，函数检查是否越界
	for (int i = 0; i < n; ++i)
	{//函数访问
		cout << s1.at(i) << " ";
	}
	cout << endl;
	return 0;
}

在这里插入图片描述

int main()
{
	string s1("yhping");
	char cha = s1[1];

	char& chb = s1[1];//一般情况下不要以引用接收

	s1.clear();//清除函数
	s1 = "hello";
	cout << chb << endl;

	return 0;
}

在这里插入图片描述

int main()
{
	string s1("yhping");
	cout << "size: " << s1.size() << endl;
	cout << "Capt: " << s1.capacity() << endl;
	cout << "max_size: "<<s1.max_size() <<endl;
	s1.reserve(128);
	cout << "size: " << s1.size() << endl;
	cout << "Capt: " << s1.capacity() << endl;
	cout << "max_size: " << s1.max_size() << endl;
}

在这里插入图片描述

int main()
{

	string s1("yhping");
	cout << s1.size() << " " << s1.capacity() << endl;
	s1.reserve(200);//正常情况每一次空间不够的时候扩容，我们现在直接一次性给200个字节空间，不需要反复的对空间进行操作
	for (int i = 0; i < 10; ++i)
	{
		s1 += "hello";
		cout << s1.size() << " " << s1.capacity() << endl;
	}
}

在这里插入图片描述

#include<vector>
class Object
{
private:
	int value;
public:
	Object(int x = 0) :value(x) { cout << "Object" << endl; }
	Object(const Object& obj) :value(obj.value) { cout << "Object &" << endl; }
	Object(Object&& obj) :value(obj.value) { cout << "move Object&&" << endl; }
	Object& operator=(const Object& obj)
	{
		value = obj.value;
		cout << "operator=" << endl;
		return *this;
	}
	Object& operator=(const Object&& obj)
	{
		value = obj.value;
		cout << "operator=" << endl;
		return *this;
	}
	~Object()
	{
		cout << "~Object" << endl;
	}
};
int main()
{
	vector<Object> vecobj;

	for (int i = 0; i < 5; ++i)
	{
		vecobj.push_back(Object(10));
		cout << vecobj.size() << endl;
		cout << vecobj.capacity() << endl;
	}
	return 0;
}

反复的扩容导致产生更多的构造和析构函数并且产生了更多的对象
增空间将原来的对象挪到新空间，在释放原来的旧空间
在这里插入图片描述

int main()
{
	vector<Object> vecobj;
	vecobj.reserve(200);
	for (int i = 0; i < 5; ++i)
	{
		vecobj.push_back(Object(10));
		cout << vecobj.size() << endl;
		cout << vecobj.capacity() << endl;
	}
	return 0;
}

在这里插入图片描述

随机性迭代器和双向迭代器的区别

int main()
{
	vector<int>ivec = { 12,2,3,34,45 };
	//随机性迭代器
	vector<int>::iterator it = ivec.begin();
	it++;
	it += 5;
	list<int>ilist = { 12,2,3,34,45 };
	//双向迭代器
	list<int>::iterator i = ilist.begin();
	i++;
	i += 5;//Erro链表不能
	return 0;
}