C++編寫字符串類CNString，該類有默認構造函數、類的拷貝函數、類的析構函數及運算符重載

編碼實現字符串類CNString，該類有默認構造函數、類的拷貝函數、類的析構函數及運算符重載，需實現以下“=”運算符、“+”運算、“[]”運算符、“<”運算符及“>”運算符及“==”運算符

以下為各個運算符的運算效果的詳細說明：

a)     字符串“=”重載運算符

CNStringstr1("abc ");

CNString str2 = str1;

b)    字符串“+”運算

CNStringstr1("abc");

CNStringstr2("efg ");

       str1 = str1 + str2;      

c)     字符串“[]”運算

CNString nstring1("abc");

cout<< nstring1[0] ;// 則屏幕顯示a

cout<< nstring1[2] ; // 則屏幕顯示c

d)    “<”運算符

CNStringstr1("abc");

CNStringstr2("efg");

if (str1 <str2 ){

cout<<“str1<str2”<<endl;

}

e)     “>”運算符

CNStringstr1("abc");

CNStringstr2("efg");

if (str1 >str2 ){

cout<<“str1>str2”<<endl;

}

f)      “==”運算符

CNStringstr1("abc");

CNStringstr2("efg");

if (str1 == str2){

cout<<“str1==str2”<<endl;

}

代碼實現：

#include<iostream>
#include<string.h>
using namespace std;

class CNString
{
    private:
        char *str_F;
    public:
        CNString(){str_F=NULL;};//默認構造函數
        CNString(char *str);//有參構造函數
        CNString(const CNString &other);//類的拷貝函數
        ~CNString();//類的析構函數
        CNString &operator=(const CNString &obj);//"="號重載
        CNString &operator+(const CNString &obj);//"+"號重載
        char& operator[](int i);//"[]"號重載
        bool operator<(const CNString &obj);//"<"號重載
        bool operator>(const CNString &obj);//">"號重載
        bool operator==(const CNString &obj);//"=="號重載
        void print()//打印str_F的結果
        {
            cout<<str_F<<endl;
        }
};
CNString::CNString(char *str)
{
    str_F = new char(strlen(str)+1);
    if(str_F!=0) strcpy(str_F,str);
}
CNString::CNString(const CNString &obj)
{
    str_F = new char(strlen(obj.str_F)+1);
    if(str_F!=0) strcpy(str_F,obj.str_F);
}
CNString::~CNString()
{
    delete []str_F;
}
CNString & CNString::operator=(const CNString &obj)
{
    char * tem=new char(strlen(obj.str_F)+1);
    strcpy(tem,obj.str_F);
    str_F=tem;
    delete[]tem;
    return *this;
}
CNString & CNString::operator+(const CNString &obj)
{
    strcat(str_F,obj.str_F);
    return *this;
}
char &CNString::operator[](int i)
{
    return str_F[i];
}
bool CNString::operator<(const CNString &obj)
{
    int c = strcmp(str_F,obj.str_F);
    if(c<0) return true;
    else return false;
}
bool CNString::operator>(const CNString &obj)
{
    int c = strcmp(str_F,obj.str_F);
    if(c>0) return true;
    else return false;
}
bool CNString::operator==(const CNString &obj)
{
    int c = strcmp(str_F,obj.str_F);
    if(c==0) return true;
    else return false;
}
int main()
{
    CNString str1("abc ");
    CNString str2("edf");
    CNString str3;
    cout<<"實現運算符+和=重載后："<<endl;
    str3 = str1 + str2;
    str3.print();
    cout<<"實現運算符[]重載后："<<endl;
    CNString nstring1("abc");
    cout<<nstring1[0]<<endl;
    cout<<"實現運算符'<' '>' '=='重載后："<<endl;
    if (str1 <str2 )
    {
        cout<<"str1<str2"<<endl;
    }
    if (str1 >str2 )
    {
        cout<<"str1>str2"<<endl;
    }
    if(str1==str2)
    {
        cout<<"str1==str2"<<endl;
    }
    return 0;
}

實現效果圖：