1 //字符串类的设计  2 //1.字符串类String能与C语言的字符串兼容使用  3 //2.重载逻辑等于运算符(==)  4 //3.字符串操作包括取字符串长度和取子串  5 #include
     
        6 #include
      
         7 #include
       
          8 class String{  9     private: 10         char *str; 11         int size; 12     public: 13 //        String(); 14         String(char *s=""); 15         String(const String &s); 16         ~String(); 17  18         int Length()const; 19         String SubStr(int pos,int length); 20  21         String &operator=(const String &s); 22         String &operator=(char *s); 23  24         int operator==(const String &s)const; 25         int operator==(char *s)const; 26  27         friend int operator==(char *strL,const String &strR); 28 }; 29  30 //String::String(){} 31 String::String(char *s){ 32     this->size=strlen(s)+1; 33     str=new char[size]; 34     strcpy(str,s); 35 } 36  37 String::String(const String &s){ 38     this->size=s.size;     39     str=new char[size]; 40     if(str==NULL){ 41         exit(0); 42     } 43     for(int i=0;i
        
         str[i]=s.str[i]; 45     } 46 } 47  48 String::~String(){ 49     delete []this->str; 50 } 51  52  53 int String::Length()const{ 54     return this->size; 55 } 56  57 String String::SubStr(int pos,int length){ 58     int charsLeft=size-pos-1; 59     String temp; 60     char *p,*q; 61  62     if(pos>=size-1){ 63         return temp; 64     } 65     if(length>charsLeft){
   //长度不能超出范围 66         length=charsLeft; 67     } 68     delete []temp.str; 69      70     temp.str=new char[length+1]; 71  72     p=temp.str; 73     q=&this->str[pos]; 74  75     for(int i=0;i
         
          size!=s.size){ 87         delete []str; 88         this->str=new char[s.size]; 89         size=s.size; 90     } 91     for(int i=0;i
          
           str[i]=s.str[i]; 93 } 94 return *this; 95 96 } 97 98 String &String::operator=(char *s){ 99 int length=strlen(s);100 if(this->size!=length){101 delete []this->str;102 str=new char[length+1];103 this->size=length+1;104 }105 strcpy(this->str,s);106 return *this;107 }108 109 int String::operator==(const String &s)const{ //String类和String类相比较110 return strcmp(this->str,s.str)==0;111 }112 int String::operator==(char *s)const{ //String类和C语言字符串比较113 return strcmp(this->str,s)==0;114 }115 116 int operator==(char *strL,const String &strR){ //C预压字符串和String类比较117 return strcmp(strL,strR.str)==0;118 }119 120 int main(){121 122 String str1("Data Structure");123 String str2("Structure");124 String str3,str4,str5;125 126 cout<
           
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