重写string类

待我称王封你为后i 2022-02-28 08:33 253阅读 0赞

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。

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`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 ;
        }   
    }