#pragma once
#include 
   
     #include 
    
      #define _SIZE_ 100 using namespace std; class Count { public: Count() :count(1){} void add() { count++; } void dec() { count--; } int getcount() { return count; } private: int count; }; class String { public: String(const char *s = "") { copy(ptr,s); } String(const String &s) { copy(ptr,s.ptr); counT.add(); } String& operator=(const String& s) { if (this != &s) { String tmp(s.ptr); char *temp = tmp.ptr; tmp.ptr = ptr; ptr = temp;//内存安全。 } return *this; } ~String() { if (counT.getcount() == 1) { cout << ptr << " :del" << endl; delete[]ptr; } } friend ostream& operator<<(ostream& os, String &s) { os << s.ptr; return os; } friend istream& operator>>(istream& is, String &s) { char buf[_SIZE_]; is >> buf; s.copy(s.ptr,buf); return is; } String& operator += (const String &s) { char *buf = new char[strlen(ptr) + strlen(s.ptr) + 1]; strcpy(buf, ptr); strcat(buf,s.ptr); copy(ptr,buf); return *this; } String& operator +=(const char *str) { char *buf = new char[strlen(ptr) + strlen(str) + 1]; strcpy(buf,ptr); strcat(buf,str); copy(ptr,buf); return *this; } bool operator != (const String &s) { return strcmp(ptr,s.ptr); } bool operator ==(const String &s) { return !strcmp(ptr,s.ptr); } private: void copy(char *&p,const char *s) { p = new char[strlen(s) + 1]; strcpy(p,s); } private: char *ptr; Count counT; }; 
    
   

#include 
   
     #include "String.h" using namespace std; int main() { String s("123"); String s1("456"); s += s1; return 0; }
   

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