Deep copy of String class (2 kinds) and shallow copy (3 kinds)

#include <iostream>using namespace std;//deep copy://class string//{//public:////default construction//string ( Char *string= "")//:_str (New char[strlen (String) +1])//{//strcpy (_str, string);//}//// If the copy constructor or assignment constructor is not written, the system default copy is a shallow copy of the////initialization list, if it is not written, if it is a base type, it is initialized to a random value, and the custom type is tuned to the constructor//string (const string&  s)//:_str (New char[strlen (S._STR) +1])//{//strcpy (_STR,&NBSP;S._STR);//}////string&    operator =  (const string& s)//{//if (this!=&s)//       {//      delete[] _str;//will not be empty, no judgment, minimum string ""//  _str =  new char[strlen (S._STR)  + 1];//  strcpy (_STR,&NBSP;S._STR);// }//return  *this;//}//~string ()//{//delete[] _str;//}//void display ()//{//cout << _str  << endl;//}//private://char* _str;//};//class  string//{//// By calling the default constructor write-copy construction and assignment operator overloading//public://string (char* string =  "")//:_string (New char[strlen (String)  + 1])//{//strcpy (_string, string);// }//string (string& s)//:_string (NULL)//need to set pointer is empty, otherwise the pointer random value will be destroyed//{//string tmp (s._string);//// Using the TMP out-of-scope destructors, destroying the open memory, this function does not need//swap (_string, s._string);//must be two operands of the same type, so parameter parameters should not be const//}//string&  Operator= (string s)//Use Copy construction assignment//{//      //do not need to judge This==&s, here is copy construction S, address must be different Swap (_string, s._string);//return *this;////uses the S-destructor to destroy the *this of the _string pointer that was originally opened.//}////   String& operator= (const string& s)////  {////if  (this != & s)////{////string tmp (s);////swap (_string, tmp._string);////}////return *this;////}////}// Two-way assignment operator overloading//~string ()//{//if  (_string)//delete[] _string;//}//void display ()//{//cout  << _string << endl;//}//private://char* _string;//};//Shallow Copy//class string// {////static variable, this method restricts only the pointer to the copy construction object/public://string (char* string =  "")//:_string (New char[strlen (String)  + 1])//{// scount = 1;//strcpy (_string, string);//}//string (const string& s)//:_string (s._ String)//initialization list cannot be a static variable//{//scount = ++scount;//}//string& operator= (const string&  s)//{////can only be used with one of the same member pointers, without defining an assignment overload//}//~string ()//{//if  (--scount == 0)//{//delete[]  _string;//}////cout << scount << endl;//}//void display ()//{//cout  << _string << endl;////cout << scount << endl;//}// private://char* _string;//static int  scount;//};//int string::scount = 0;/ /class string//{////Each object defines a number of objects that store the same pointer//public://string (char* string= "")//:_string (New char [Strlen (String) +1]),//scount (New int (1))//{//strcpy (_string, string);//}//string (const string & s)//:_String (s._string),//scount (S.scount)//{//++ (*scount);//}//string& operator= (const string&  s)//{//if  (this != &s)//{//delete (*this);//_string = s._string;//scount  = s.scount;//++ (*scount);//}//return *this;//}//void delete (String& s)//{//if   (--(*s.scount)  == 0)//{//delete scount;//delete[] _string;//}//}//~string ()//{// Delete (*this);//}//void display ()//{//cout << _string << endl;//}// private://char* _string;//int *scount;//};//class string//{////gives the front more than 4 bytes to store an object that refers to the same member pointer//public ://string (char* str =  "")//:_str (New char[strlen (str)  + 5])//{//* ((int *) _ STR)  = 1;//_str = _str + 4;//strcpy (_STR,&NBSP;STR);//}//String (const  String& s)//:_str (S._STR)//{//++ (* (int *) (_str-4));//}//string& operator= (const  string& s)//{//if  (thiS != &s)//{//            delete (* this);//_str = s._str;//++ (* (int *) (_str-4));//}//return  *this;//}//~string ()//{// cout << * ((int*) (_str - 4))  << endl;//delete (*this);//      //}//void delete (String& s)//{//if  (--(* (int *) (_str-4)) == 0)// {//_str -= 4;//delete[]  _str;//}//}//void display ()//{//cout << _str  << endl;//cout << * (int*) (_str - 4)  << endl;////}// Private://char* _str;//};void test1 () {string s1 ("abcdef"); S1. Display (); STRING&NBSP;S2 (s1); S2. Display (); STRING&NBSP;S3 ("abc"); S3. Display (); S3 = s1;s3. Display ();} Int main () {Test1 (); System ("pause"); return 0;}

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Deep copy of String class (2 kinds) and shallow copy (3 kinds)