仿照string类，完成myString 类

#include <iostream>
#include <cstring>
using namespace std;
class myString
{
private:
    char *str;          //记录c风格的字符串
    int size;            //记录字符串的实际长度
public:
    //无参构造
    myString():size(10)
    {
        str = new char[size];         //构造出一个长度为10的字符串
        strcpy(str,"");         //赋值为空串
    }
    //有参构造
    myString(const char *s)          //string  s("hello world")
    {
        size = strlen(s);
        str = new char[size+1];
        strcpy(str, s);
    }
    
    //拷贝构造
    myString(const myString &other):size(other.size)
    {
        str=new char(other.size+1);
        strcpy(str, other.str);
    }
    //析构函数
    ~myString()
    {
        delete str;
        cout<<"析构函数"<<endl;
    }
    //拷贝赋值函数
    myString & operator=(const myString &other)
    {
        if(this!=&other)
        {
            this->size=other.size;
            if(this->str!=NULL)
            {
                delete this->str;
            }
            this->str=new char(*other.str);
        }
        cout<<"拷贝赋值"<<endl;
        return *this;
    }
    //判空函数
    bool myemp()const
    {
        return strlen(str)==0;
    }
    //size函数
    int mysize()const
    {
        return strlen(this->str)+1;
    }
    //c_str函数
    char *C_str()
    {
        return this->str;
    }
    //at函数
    char &at(int pos)
    {
        if(pos>this->size || pos<0)
        {
            cout<<"pos输入错误 "<<endl;
            return this->str[0];
        }
        return this->str[pos-1];
    }
    //加号运算符重载
    const myString operator+ ( const myString &R)const
    {
        myString s;
        s.str=strcat(this->str,R.str);
        s.size=this->size+R.size;
        s.show();
        return s;
    }
    //加等于运算符重载
    myString operator+= (const myString &R)
    {
        strcat(this->str,R.str);
        this->size +=R.size;
        return *this;
    }
    //关系运算符重载（>）
    bool operator> ( const myString &R)const
    {
        return strcmp(this->str,R.str);
    }
    //中括号运算符重载
    char & operator[](int index)
    {
        return this->str[index-1];
    }
    void show()
    {
        cout<<str<<endl;
    }
};
int main()
{
    myString s1("hello world");
    s1.show();
    cout<<s1.at(20)<<endl;
    cout<<s1[1]<<endl;
    myString s2(s1);
    s2.show();
    s2+=s1;
    myString s3=s2;
    s3.show();
    if(s3>s1)
    {
        cout<<"************************"<<endl;
    }
    myString s4;
    cout<<s4.myemp()<<endl;
    return 0;
}