mystring.cpp

杭州电子科技大学期末考试试题,有参考价值

#include<iostream>
using namespace std;
#include<cstring>
class mystring;
 bool operator<=(const mystring&s1,const mystring&s2);
 bool operator>(const mystring&s1,const mystring&s2);
 bool operator==(const mystring&s1,const mystring&s2);
 ostream operator<<(ostream &os,const mystring& rhs);
istream operator>>(istream &is,mystring& rhs);
class mystring{
	private:
		char *str;
		int len;
		enum {CINLIM=80} ;
	public:
		mystring();
		mystring(const mystring& rhs);
		~mystring();
		mystring(const char*s);
		int length(){return len;}
		mystring& operator=(const mystring&rhs);
		mystring& operator=(const char*s);
        mystring& operator+=(const mystring& rhs);
		char& operator[](int i);
		const char& operator[](int i)const;
		friend bool operator<=(const mystring&s1,const mystring&s2);
        friend bool operator>(const mystring&s1,const mystring&s2);
		friend bool operator==(const mystring&s1,const mystring&s2);
		friend ostream operator<<(ostream &os,const mystring& rhs);
		friend istream operator>>(istream &is,mystring& rhs);

};
	mystring::mystring(){
		len=0;
		str=new char[1];
		str[0]='\0';
		}
	mystring::mystring(const mystring& rhs){
	len=rhs.len;
	str=new char[len+1];
	strcpy(str,rhs.str);
	}
	mystring::~mystring(){
	delete []str;
	str=NULL;
	len=0;
	}
	mystring::mystring(const char* s){
		len=strlen(s);
		str=new char[len+1];
		strcpy(str,s);
	}
	mystring& mystring::operator+=(const mystring& rhs){
	     len=len+rhs.len ;
		 char* temp=new char[len+1];
		 int  i;
		 for(i=0;str[i]!='\0';i++)
			 temp[i]=str[i];
		 for(int j=0;j<rhs.len ;j++)
			 temp[i+j]=rhs.str [j];
		 temp[len]='\0';
		 delete []str;
		 str=temp;
		 return *this;
    }
	mystring& mystring::operator=(const mystring& rhs){
		if(this==&rhs)  return *this;
		delete []str;
		len=rhs.len;
		str=new char[len+1];
		strcpy(str,rhs.str);
		return *this;

	}
	mystring& mystring::operator=(const char* s){
		delete []str;
		len=strlen(s);
		str=new char[len+1];
		strcpy(str,s);
		return *this;
	}
	char& mystring::operator[](int i){
		return str[i-1];
	}
	const char& mystring::operator[](int i)const{
		return str[i-1];

	}
	bool operator<=(const mystring&s1,const mystring& s2){
		return(strcmp(s1.str,s2.str)<=0);
	}
	bool operator>(const mystring&s1,const mystring& s2){
		return(strcmp(s1.str,s2.str)>0);

	}
	bool operator==(const mystring&s1,const mystring& s2){
		return(strcmp(s1.str,s2.str)==0);

	}
	ostream operator<<(ostream &os,const mystring& rhs){
		os<<rhs.str;
		return os;
	}
		istream operator>>(istream &is,mystring& rhs){
		char temp[mystring::CINLIM];
		is.get(temp,mystring::CINLIM);
		if(is){
			delete []rhs.str;
			rhs.len=mystring::CINLIM;
			rhs.str=new char[mystring::CINLIM+1];
			strcpy(rhs.str,temp);
		}
			
		while(is&&is.get()!='\n')
			continue;
			return is;
	}

int main(){
	mystring s1,s2;
	s1="3111111";
	s2="1223233";
	cout<<"s1="<<s1<<endl;
	s2+=s1;
	cout<<"s2="<<s2<<endl;
	cout<<(s1<=s2)<<endl;
    cout<<s2.length ()<<endl;
	return 0;
}