day 0912

#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)
    {
        size = strlen(s);
        str =new char[size+1];
        strcpy(str,s);
    }
    //拷贝构造
    myString(const myString &other)
    {
        size = strlen(other.str);
        str =new char[size+1];
        strcpy(str,other.str);
    }
    //析构函数
    ~myString ()
    {
        delete str;
        str = nullptr;
    }
    //拷贝赋值函数
    myString & operator=(const myString &other)
    {
        if(this != &other)
        {
            if(this->str != NULL)
            {
                delete str;
            }
            this->str = new char[strlen(other.str)+1];
            strcpy(str,other.str);
        }
        return *this;
    }
    //判空函数
    bool str_empty()
    {
        return str == nullptr;
    }
    //size函数
    int str_size()
    {
        return size;
    }
    //c_str函数
       char *c_str()
       {
           char *c_string = new char[size +1];
           strcpy(c_string, str);
           return c_string;
       }
    //at函数
    char &at(int pos)
    {
        if(pos<0||pos>size-1)
            return*str;
            return *(str+pos);
    }
    //加号运算符重载
    const myString operator+(const myString &s)
    {
        myString  tmp;
        tmp.size = size + s.size;
        tmp.str = new char[tmp.size+1];
        strcpy(tmp.str,str);
        char *dstr = tmp.str + size;
        strcpy(dstr, s.str);
        dstr = nullptr;
        return tmp;
    }
    //加等于运算符重载
    const myString operator+=(const myString &s)
    {
        myString tmp(*this);
        size = tmp.size + s.size;
        delete str;
        str = new char[size+1];
        strcpy(str,tmp.str);
        char *dstr = str + tmp.size;
        strcpy(dstr, s.str);
        dstr = nullptr;
        return *this;
    }
    //关系运算符重载（>)
    bool operator >(const myString &s)
    {
        int i=0;
        for(;(*(str+i)==*(s.str+i) && *(str+i)!=0 && *(s.str+i)!=0);i++);
        return *(str+i)-*(s.str+i)>0;
    }
    //中括号运算符重载
    char &operator[](int pos)
    {
        if(pos<0||pos>size-1)
            return *str;
        return *(str+pos);
    }
    //定义成员函数
    void show()
    {
        cout<<str<<endl;
    }
};

int main()
{
   myString s1("hello ");
   myString s2("world");
   myString s3;
   s3 = s1+s2;
   s3.show();

   myString s4;
   s4 = s3;
   s4.show();

   s1+=s2;
   s1.show();

   s1[0]='H';
   s1.show();

   s1.at(6)='W';
   s1.show();
   return 0;
}