指针权限，new与delete，类与对象，函数模板，类模板的用法

指针权限 用法

void Print(const char* SecretPointer)
{cout << "绝密指令为：";cout << SecretPointer << endl;
}void Change(int& number, int* const FixedPointer)
{cout << "更换站台数字为：";cin >> number;cout << *FixedPointer << endl;
}int main()
{char* SecretPointer_01 = (char*)malloc(sizeof(char) * 20);cout << "请输入绝密指令：";cin >> SecretPointer_01;const char* SecretPointer = SecretPointer_01;Print(SecretPointer);int number = 100;int* const FixedPointer = &number;cout << "原站台数字为：" << *FixedPointer << endl;Change(number, FixedPointer);return 0;
}

new与delete 用法

#include <iostream>
using namespace std;int* CreateSpace1(int*&  PointerOfSum1)
{PointerOfSum1 = new int(0);     // 1 return new int[5]{ 1,2,3,4,5 };     //  2
}void AddArray1(int*& PointerOfSum1, int*& PointerOfArray1)
{for (int i = 0; i < 5; i++){(*PointerOfSum1) += (*(PointerOfArray1 + i));}
}// class StupidPerson
{
public:StupidPerson(int IQ = 10):_IQ(IQ){}int GetIQ(){return _IQ;}
private:int _IQ;
};StupidPerson* CreateSpace2(int*& PointerOfSum2)
{PointerOfSum2 = new int(0);return new StupidPerson[5];    // 3
}void AddArray2(int*& PointerOfSum2, StupidPerson*& PointerOfArray2)
{for (int i = 0; i < 5; i++){(*PointerOfSum2) += ((*(PointerOfArray2 + i)).GetIQ());}
}//class SmartPerson
{
public:SmartPerson(int IQ = 100):_IQ(IQ){}~SmartPerson(){_IQ = 0;}int GetIQ(){return _IQ;}
private:int _IQ;
};SmartPerson* CreateSpace3(int*& PointerOfSum3)
{PointerOfSum3 = new int(0);return new SmartPerson[5]{ SmartPerson(),SmartPerson(101),SmartPerson(102) ,SmartPerson(99) ,SmartPerson(107) };   // 4
}void AddArray3(int*& PointerOfSum3, SmartPerson*& PointerOfArray3)
{for (int i = 0; i < 5; i++){(*PointerOfSum3) += ((*(PointerOfArray3 + i)).GetIQ());}
}int main()
{int* PointerOfSum1 = nullptr;int* PointerOfArray1 = CreateSpace1(PointerOfSum1);AddArray1(PointerOfSum1, PointerOfArray1);cout << "总和为：" << (*PointerOfSum1) << endl;delete PointerOfSum1;   // 5delete[] PointerOfArray1;    //  6//int* PointerOfSum2 = nullptr;StupidPerson* PointerOfArray2 = CreateSpace2(PointerOfSum2);AddArray2(PointerOfSum2, PointerOfArray2);cout << "IQ总和为：" << (*PointerOfSum2) << endl;delete PointerOfSum2;delete[] PointerOfArray2;//int* PointerOfSum3 = nullptr;SmartPerson* PointerOfArray3 = CreateSpace3(PointerOfSum3);AddArray3(PointerOfSum3, PointerOfArray3);cout << "IQ总和为：" << (*PointerOfSum3) << endl;delete PointerOfSum3;delete[] PointerOfArray3;//SmartPerson* ps = (SmartPerson*)malloc(sizeof(SmartPerson) * 10);cout << "内存池已经创建完成！" << endl;new(ps)SmartPerson(110);    //  7new(ps + 1)SmartPerson(103);cout << "第一个人智商为：" << ps->GetIQ() << endl;cout << "第二个人智商为：" << (ps + 1)->GetIQ() << endl;ps->~SmartPerson();   // 8(ps + 1)->~SmartPerson();return 0;
}

类与对象 用法

test.h#include <iostream>
using namespace std;class Country
{friend class Citizen;friend istream& operator>>(istream& cin, Country& country);friend ostream& operator<<(ostream& cout, const Country& country);
public://构造函数Country();//拷贝构造函数Country(const Country& other);//析构函数~Country();//赋值运算符重载Country& operator=(const Country& other);
private:char* _countryname;char* _capital;
};
//流插入运算符重载
istream& operator>>(istream& cin, Country& country);
//流提取运算符重载
ostream& operator<<(ostream& cout, const Country& country);//class Citizen
{friend int operator>(const Citizen& c1, const Citizen& c2);friend istream& operator>>(istream& cin, Citizen& citizen);friend ostream& operator<<(ostream& cout, const Citizen& citizen);
public://构造函数explicit Citizen(bool iscriminal = false);//拷贝构造函数Citizen(const Citizen& other);//析构函数~Citizen();//赋值运算符重载Citizen& operator=(const Citizen& other);//前置++运算符重载Citizen& operator++();//后置++运算符重载Citizen operator++(int);//普通运算符重载Citizen& operator-(int num);//静态成员函数static int GetTotalCitizen();//友元类的跨类访问void GetCountry();
private://成员变量char* _personalname;int _age;Country _nationality;bool _iscriminal;int _creditscore;const int _maxcreditscore;//类的静态区成员变量static int _totalcitizen;
};
//普通运算符重载
int operator>(const Citizen& c1, const Citizen& c2);
//流插入运算符重载
istream& operator>>(istream& cin, Citizen& citizen);
//流提取运算符重载
ostream& operator<<(ostream& cout, const Citizen& citizen);

//func.cpp#include "test.h"//Country类相关
Country::Country()
{_countryname = new char[20]{ '\0' };_capital = new char[20]{ '\0' };
}Country::Country(const Country& other)
{_countryname = new char[20]{ '\0' };_capital = new char[20]{ '\0' };memcpy(_countryname, other._countryname, sizeof(char) * 20);memcpy(_capital, other._capital, sizeof(char) * 20);
}Country::~Country()
{delete[] _countryname;delete[] _capital;
}Country& Country::operator=(const Country& other)
{if (&other != this){memcpy(_countryname, other._countryname, sizeof(char) * 20);memcpy(_capital, other._capital, sizeof(char) * 20);}return *this;
}istream& operator>>(istream& cin, Country& country)
{cin >> country._countryname >> country._capital;return cin;
}ostream& operator<<(ostream& cout, const Country& country)
{cout << country._countryname << " " << country._capital;return cout;
}//Citizen类相关
Citizen::Citizen(bool iscriminal):_age(0),_nationality(),_iscriminal(iscriminal),_creditscore(0),_maxcreditscore(100)
{_personalname = new char[20]{ '\0' };_totalcitizen++;
}Citizen::Citizen(const Citizen& other):_age(other._age), _nationality(other._nationality), _iscriminal(other._iscriminal), _creditscore(other._creditscore), _maxcreditscore(other._maxcreditscore)
{_personalname = new char[20]{ '\0' };memcpy(_personalname, other._personalname, sizeof(char) * 20);_totalcitizen++;
}Citizen::~Citizen()
{delete[] _personalname;_totalcitizen--;
}Citizen& Citizen::operator=(const Citizen& other)
{if (&other != this){_age = other._age;_nationality = other._nationality;_iscriminal = other._iscriminal;_creditscore = other._creditscore;memcpy(_personalname, other._personalname, sizeof(char) * 20);}return *this;
}Citizen& Citizen::operator++()
{if (_creditscore < _maxcreditscore){_creditscore++;}return *this;
}Citizen Citizen::operator++(int)
{Citizen tmp(*this);if (_creditscore < _maxcreditscore){_creditscore++;}return tmp;
}Citizen& Citizen::operator-(int num)
{if (_creditscore > 0){_creditscore -= num;if (_creditscore < 0){_creditscore = 0;}}return *this;
}int operator>(const Citizen& c1, const Citizen& c2)
{if (c1._creditscore > c2._creditscore){return 1;}else if (c1._creditscore < c2._creditscore){return 2;}else{return 0;}
}istream& operator>>(istream& cin, Citizen& citizen)
{cin >> citizen._personalname >> citizen._age >> citizen._nationality>> citizen._iscriminal >> citizen._creditscore;return cin;
}ostream& operator<<(ostream& cout, const Citizen& citizen)
{cout << citizen._personalname << " " << citizen._age << " " << citizen._nationality<< " " << citizen._iscriminal << " " << citizen._creditscore;return cout;
}int Citizen::GetTotalCitizen()
{return _totalcitizen;
}void Citizen::GetCountry()
{cout << _nationality._countryname << " " << _nationality._capital << endl;
}//类的静态区成员变量定义
int Citizen::_totalcitizen = 0;

//test.cpp#include "test.h"int main()
{Citizen Shen(0);cin >> Shen;cout << Shen << endl;Citizen Jun(Shen);cout << Jun << endl;Citizen Elon(0);cin >> Elon;cout << Elon << endl;cout << "此时人数：" << Citizen::GetTotalCitizen() << endl;return 0;
}

函数模板 用法

// test.h#include <iostream>
using namespace std;template <typename T>
void Swap(T& a, T& b)
{T tmp = a;a = b;b = tmp;
}template <typename T1, typename T2, typename T3>
void Print(const T1& a, const T2& b, const T3& c)
{cout << a << " " << b << " " << c << endl;
}

// test.cpp
#include "test.h"int main()
{int x = 1;int y = 2;char m = 'x';char n = 'y';cout << "交换前：" << endl;cout << x << " " << y << endl;cout << m << " " << n << endl;Swap(x, y);Swap(m, n);cout << "交换后：" << endl;cout << x << " " << y << endl;cout << m << " " << n << endl;//const char* pointer = "根据ASCII码表对应的(值/字符)为";char obj1 = 'A';int obj2 = 65;Print(obj1, pointer, obj2);Print<int, const char*, char>(obj1, pointer, obj2);     return 0;
}

类模板 用法

// test.h
#include <iostream>
using namespace std;template <typename T>
class Person
{friend istream& operator>>(istream& cin, Person<T>& person){cin >> person._name >> *(person._luckysymbol);return cin;}friend ostream& operator<<(ostream& cout, Person<T>& person){cout << person._name << " " << *(person._luckysymbol);return cout;}
public:Person();Person(const Person& other);~Person();Person& operator=(const Person& other);
private:char* _name;T* _luckysymbol;
};template <typename T>
Person<T>::Person()
{_name = new char[20]{ 0 };_luckysymbol = new T(0);
}template <typename T>
Person<T>::Person(const Person& other):_name(new char[20]{ 0 }), _luckysymbol(new T(0))
{memcpy(_name, other._name, sizeof(char) * 20);*_luckysymbol = *(other._luckysymbol);
}template <typename T>
Person<T>::~Person()
{delete _luckysymbol;delete[] _name;
}template <typename T>
Person<T>& Person<T>::operator=(const Person& other)
{if (&other != this){memcpy(_name, other._name, sizeof(char) * 20);*_luckysymbol = *(other._luckysymbol);}return  *this;
}

// test.cpp
#include "test.h"int main()
{Person<int> Shen;Person<char> Hu;Person<double> Ye;cin >> Shen >> Hu >> Ye;Person<int> Junyang(Shen);  Person<char> Yao;   Yao = Hu;   cout << Shen << endl;cout << Hu << endl;cout << Ye << endl;cout << Junyang << endl;cout << Yao << endl;return 0;
}