实现string类的操作符重载 + = > < == != >> <<

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//MyString.h#pragma  once#include <iostream>using namespace std;class MyString{private:char *m_ptr;//内存空间public:MyString(const char *str=NULL);//构造函数MyString(const MyString& obj); //拷贝构造函数~MyString();  //析构函数public:// + = > < == != >> <<MyString operator+(const MyString& obj);  //连接MyString &operator=(const MyString& obj);  //赋值bool operator>(const MyString& obj);  //比较大小bool operator<(const MyString& obj);  //比较大小bool operator==(const MyString& obj);  //比较大小bool operator!=(const MyString& obj);  //比较大小friend istream& operator>>(istream& in, MyString &obj); //输入流friend ostream& operator<<(ostream& out, const MyString& obj);  //输出流};

//MyString.cpp#define _CRT_SECURE_NO_WARNINGS#include "MyString.h"MyString::MyString(const char *str)//构造函数{if (str == NULL){this->m_ptr = new char[1];this->m_ptr[0] = '\0';}else{this->m_ptr = new char[strlen(str)+1];strcpy(this->m_ptr, str);}}MyString::MyString(const MyString& obj) //拷贝构造函数{this->m_ptr = new char[strlen(obj.m_ptr) + 1];strcpy(this->m_ptr, obj.m_ptr);}MyString::~MyString()  //析构函数{delete[] m_ptr;this->m_ptr = NULL;}MyString MyString::operator+(const MyString& obj)  //连接{MyString tmp;delete[] tmp.m_ptr;tmp.m_ptr = new char[strlen(this->m_ptr) + strlen(obj.m_ptr) + 1];sprintf(tmp.m_ptr, "%s%s", this->m_ptr, obj.m_ptr);return tmp;}MyString &MyString::operator=(const MyString& obj)  //赋值{if (this->m_ptr != NULL){delete[] m_ptr;this->m_ptr = NULL;}this->m_ptr = new char[strlen(obj.m_ptr) + 1];strcpy(this->m_ptr, obj.m_ptr);return *this;}bool MyString::operator>(const MyString& obj)  //比较大小{if (-1 == strcmp(this->m_ptr, obj.m_ptr)){return true;}else{return false;}}bool MyString::operator<(const MyString& obj) //比较大小{if (1 == strcmp(this->m_ptr, obj.m_ptr)){return true;}else{return false;}}bool MyString::operator==(const MyString& obj)  //比较大小{if (0 == strcmp(this->m_ptr, obj.m_ptr)){return true;}else{return false;}}bool MyString::operator!=(const MyString& obj)  //比较大小{return !(*this==obj);}ostream& operator<<(ostream& out, const MyString& obj) //输出流{out << obj.m_ptr;return out;}istream& operator>>(istream& in, MyString &obj) //输入流{char tmp[1024 * 10];memset(tmp, 0, sizeof(tmp));in >> tmp;if (obj.m_ptr != NULL){delete[] obj.m_ptr;obj.m_ptr = NULL;}obj.m_ptr = new char[strlen(tmp) + 1];strcpy(obj.m_ptr, tmp);return in;}

//MyStringTest.cpp#include "MyString.h"using namespace std;void run(){MyString s1("abd");MyString s2("hello");MyString s3 = s2;MyString s4;//s1 = s2;s4 = s1 + s2;cout << s4 << endl;if (s1==s2){cout << "相等" << endl;}else{cout << "不相等" << endl;if (s1 < s2){cout << "s1<s2" << endl;}else if (s1 > s2){cout << "s1>s2" << endl;}}cout << s1 <<","<< s2 << endl;cin >> s4;cout << s4 << endl;}void main(){run();system("pause");}

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