mystring类实现的都是些常用的操作，字符串的累加，各种形式的赋值，迭代器的自增，自减等！通过写这个感觉主要熟悉了c++运算符重载的原理，另外就是熟悉了string对象的内置常用方法。
头文件
//mystring.h
#pragma once
#include<string.h>
#include<strings.h>
#include<stdlib.h>
#include<iostream>
using namespace std;
class mystring
{
friend ostream&operator<<(ostream&out,const mystring&s);
friend istream&operator>>(istream&in,mystring&s);
private:
char *p;
public:
int len;
class iterator ;
mystring();
mystring(const char *s);
mystring(mystring const&s);
~mystring();
public :
char operator[](const int i);
mystring& operator=(const mystring&s);
mystring& operator=(const char * s);
bool operator==(mystring const&s);
bool operator==(const char *s);
mystring& operator+=(const char*s) ;
mystring& operator+=(mystring const s) ;
bool operator!=(const char *s);
bool operator!=(const mystring&s);
bool operator<(const mystring&s);
bool operator<(const char *s);
bool operator>(const mystring &s);
public :
char* c_str() ;
int length();
bool operator>(const char *s);
int indexof(const char& s);
int lastIndexOf(const char &s);
char* substr(int start, int end);
char* substr(int start) ;
char* data();
public :
iterator end()const
{
if(this->len == 0)
{
throw exception() ;
}
int len = strlen(this->p) ;
return iterator(this, len) ;
}
iterator begin()const
{
if(this->len == 0)
{
throw exception() ;
}
int s = 0 ;
iterator its = iterator(this, s) ;
return its ;
}
public :
//迭代器
class iterator{
public :
mystring* it;
int index ;
public :
iterator(){ it = new mystring() ; index = 0 ;}
iterator(const mystring* str, int i)
{
if(i > str->len || i < 0)
{
throw exception() ;
}
it = new mystring(*str) ;
it->len = str->len ;
this->index = i ;
}
~iterator()
{
delete it ;
it = NULL ;
index = 0 ;
}
public :
bool operator==(iterator const its)
{
if(its.index == this->index&&its.it == this->it)
{
return true ;
}
return false ;
}
//此处记一坑
//返回值为迭代器的引用类型而不是迭代器对象！！！
iterator& operator=(iterator const s)
{
if(s.it == NULL)
{
throw exception();
}
this->index = s.index ;
this->it = new mystring(*(s.it)) ;
return *this ;
}
iterator& operator --()
{
if(it->len < 0)
{
throw exception() ;
}
else
{
this->index -- ;
return *this ;
}
}
bool operator!=(iterator s)
{
return this->index == s.index?false:true ;
}
//i++操作
void operator++()
{
if(it->len-1 == this->index)
{
throw exception() ;
}
++this->index ;
}
//++i操作
void operator++(int i)
{
i = 1 ;
if(strlen(this->it->p) < (size_t)this->index)
{
throw exception() ;
}
this->index += i ;
}
char operator*()
{
if(it == NULL)
{
throw exception() ;
}
return this->it->p[index];
}
};
};
mystring& mystring::operator+=(mystring const s)
{
if(s.len == 0)
{
return *this ;
}
else
{
char* q = new char[strlen(s.p)+strlen(p)+1] ;
strcpy(q, p);
strcat(q, s.p) ;
free(p) ;
p = new char[strlen(q)+1];
strcpy(p, q) ;
free(q) ;
return *this ;
}
}
char* mystring:: c_str()
{
return p ;
}
int mystring::lastIndexOf(const char& s){
if(len==0){
return -1;
}
for(int i=len-1;i>=0;i--){
if(p[i]==s)return i;
}
return -1;
}
int mystring::length(){
return len;
}
mystring& mystring::operator+=(const char*s)
{
if(p == NULL)
{
return *this;
}
else
{
char * q= new char[strlen(s)+strlen(p)+1];
strcpy(q, p);
strcat(q, s);
free(p);
p = new char[strlen(s)+1] ;
strcpy(p,s) ;
len = strlen(p);
free(q) ;
}
return *this ;
}
int mystring::indexof(const char&s){
for(int i=0;i<len;i++){
if(p[i]==s){
return i;
}
}
return -1;
}
bool mystring::operator!=(const mystring&s){
return strcmp(p,s.p)?true:false;
}
bool mystring ::operator!=(const char*s){
return strcmp(p,s)?true:false;
}
bool mystring::operator<(const mystring&s){
if(strcmp(p,s.p)<0){
return true;
}
else{
return false;
}
}
bool mystring::operator<(const char*s){
if(strcmp(p,s)>0){
return false;
}
else{
return true;
}
}
bool mystring::operator>(const mystring&s){
if(strcmp(p,s.p)>0){
return true;
}
else{
return false;
}
}
bool mystring::operator>(const char*s){
if(strcmp(p,s)>0){
return true;
}
return false;
}
char * mystring::data(){
return p;
}
bool mystring ::operator==(const mystring&s){
return strcmp(p,s.p)?0:1;
}
bool mystring::operator==(const char *s){
return strcmp(p,s)?0:1;
}
char mystring::operator[](const int i){
if(i>len){
cout<<"out of index"<<endl;
exit(1);
}
else{
return p[i];
}
}
ostream&operator<<(ostream& out,const mystring &s){
out<<s.p;
return out;
}
istream&operator>>(istream&in,mystring &s){
cin>>s.p;
return in;
}
mystring ::mystring(){
len = 0 ;
p = new char[len+1];
strcpy(p,"");
}
mystring::~mystring(){
len = 0;
delete[]p;
p =NULL;
}
mystring& mystring::operator=(mystring const&s){
len = s.len ;
p = new char[len+1];
strcpy(p,s.p);
return *this;
}
mystring& mystring::operator=(const char *s){
if(!strcmp(s,"")||s==NULL){
len = 0 ;
p = new char[len+1];
strcpy(p,"");
}
else{
len = strlen(s);
p = new char[len+1];
strcpy(p,s);
}
return *this;
}
char* mystring :: substr(int start, int end)
{
if((end-start) < 0|| end > len)
{
return NULL ;
}
char *q ;
q = (char* )malloc (end-start+3);
strncpy(q, p+start, end-start) ;
return q ;
}
char* mystring :: substr(int start)
{
if(start < 0 || start > len)
{
throw exception() ;
}
return p+start ;
}
mystring::mystring(const char*s){
if(!strcmp(s,"")||s==NULL){
len = 0 ;
p = new char[len+1];
}
else{
len= strlen(s);
p = new char[len+1];
strcpy(p,s);
}
}
mystring :: mystring(mystring const& s)
{
if(s.len == 0)
{
p = NULL ;
}
int len = strlen(s.p) ;
p = new char[len+1] ;
strcpy(p, s.p) ;
}
测试
#include"mystring.h"
int main()
{
mystring s = "changkec" ;
mystring ss = s ;
cout << s << endl ;
cout << s[1] <<endl;
cout<<s.substr(1,4)<<endl ;
mystring::iterator its;
for(its = s.begin(); its != s.end(); ++its)
{
std::cout << *its << endl ;
}
cout << "00000000000000000000000" <<endl ;
for(its = s.begin(); its != s.end(); its++)
{
std::cout << *its << endl ;
}
}