c++

<pre name="code" class="cpp">#include <iostream>using namespace std;class String{public:    String();     String(const char*const ch);     int getlen()const { return len;}              friend ostream&operator<<(ostream &o, const String &s)    {        o<<s.str;        return o;    }         friend istream&operator>>(istream &i, String &s)    {         i>>s.str;         return i;    }       friend bool operator<(const String&str1, const String&str2)    {        if(strcmp(str1.str, str2.str) < 0){            return 1;        }else            return 0;    }    friend bool operator>(const String&str1, const String&str2)    {        if(strcmp(str1.str, str2.str) > 0){            return 1;        }else            return 0;    }    friend bool operator==(const String&str1, const String&str2)    {        if(strcmp(str1.str, str2.str) == 0){            return 1;        }else            return 0;    }          char &operator[](unsigned short int  length);    char  operator[](unsigned short int  length)const;         String (const String&r);         String &operator=(const String &s);      private:    unsigned short int len;    char *str;};String::String(){    len = 0;    str = new char[1];    str[0] = '\0';};String::String(const char*const ch){       len = strlen(ch);    str = new char[len+1];    for(int i=0; i<len; i++){       str[i] = ch[i];    }    str[len] = '\0';}; char & String::operator[](unsigned short int length){        if(length > len){           return str[len-1];        }else{           return str[length];        }}; char String::operator[](unsigned short int length)const{        cout<<"下标运算符const执行"<<endl;        if(length > len){           return str[len-1];         }else{           return str[length];        }}; String::String (const String&rs){    len = rs.getlen();    str = new char[len+1];    for(int i=0; i<len; i++){        str[i] = rs[i];            }    str[len]='\0';    cout<<"复制构造函数完成:"<<str<<endl; }; String& String::operator=(const String &s){    cout<<"operator=执行"<<endl;    if(this == &s)    {        return *this;    }else{        delete []str;         len = s.getlen();        str = new char[len+1];        for(int i=0; i<len; i++){            str[i] = s[i];        }        str[len] = '\0';    }    return *this; } int main(){    String s1("aaa");cout<<"s1=aaa"<<endl;    String s2("bbb");cout<<"s2=bbb"<<endl;    int ch1 = s1>s2;if (ch1=1)cout<<"s1<s2"<<endl;else cout<<"s2>=s1"<<endl;String s3("aaa");cout<<"s3=aaa"<<endl;int ch3 = s1==s3;if (ch3=1)cout<<"s1s3相等"<<endl;else cout<<"并不相等"<<endl;int ch4 = s2==s3;if (ch4=1)cout<<"s2s3并不相等"<<endl;else cout<<"相等"<<endl;     return 0;}

#include<iostream.h>#include<string.h>class string{protected: char *sp;public: string(){sp=0;} string(string &); string(char *s) { sp=new char[strlen(s)+1]; strcpy(sp,s); } ~string (){if(sp)delete sp;} void show(){cout<<sp<<endl;} string & operator = (string &); friend string operator + (string &,string &); string operator - (string &); string operator - (char); int operator > (string &); };string::string(string &s){ if(s.sp){ sp=new char[strlen(s.sp)+1]; strcpy(sp,s.sp); } else sp=0;}string operator + (string &s1,string &s2){ string t; t.sp=new char[strlen(s1.sp)+strlen(s2.sp)+1]; strcpy(t.sp,s1.sp); strcat(t.sp,s2.sp); return t;}string string::operator - (string &s){ string t1=*this; char *p; while(1) { if(p=strstr(t1.sp,s.sp)) { if(strlen(t1.sp)==strlen(s.sp)) { delete t1.sp; t1.sp=0; break; } string t2; t2.sp=new char[strlen(t1.sp)-strlen(s.sp)+1]; char *p1=t1.sp,*p2=t2.sp; int i=strlen(s.sp); while(p1<p) *p2++=*p1++; while(i){p1++;i--;} while(*p2++=*p1++); t1=t2; } else break; } return t1;}string string::operator - (char s){ string t1; int i=0,flag=0; t1.sp=new char[strlen(sp)+1]; char *p1=sp,*p2=t1.sp; while(*p1) { if(*p1!=s){ *p2++=*p1++; i++; flag=1; } else p1++; } *p2='\0'; return t1;}int string::operator > (string &s){ if(strcmp(sp,s.sp)>0) { return 1; } else return 0;}string & string::operator = (string &s) { if(sp) delete sp; if(s.sp) { sp=new char[strlen(s.sp)+1]; strcpy(sp,s.sp); } else sp=0; return *this;}void main(){ string s1("southeast"),s2("as"),s3,s4,s5; s1.show(); s2.show(); s3=s1+s2; s3.show(); if(s1>s2) cout<<"s1>s2成立!"<<endl; else cout<<"s1>s2不成立!"<<endl; s4=s3-s2; s4.show(); s5=s3-'t'; s5.show();}