【面试题目】string类实现

 

// StringClass.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include<iostream>

class MyString
{
public:
    MyString();
    MyString(constchar*sz);
    MyString(const MyString &rhs);
    booloperator== (constchar* sz);
    booloperator== (const MyString &rhs);
    MyString&operator= (constchar*sz);
    MyString&operator= (const MyString &rhs);
    MyString operator+ (constchar*sz);
    MyString operator+ (const MyString &rhs);
    int size() const;
protected:
private:
    int _size;
    char* _string;
};

MyString::MyString()
{
    _size =0;
    _string =0;
}

MyString::MyString(constchar*sz)
{
    if(!sz){_size =0; _string =0;}
    _size = strlen(sz);
    _string =newchar[_size+1];
    strcpy(_string, sz);
}

MyString::MyString(const MyString &rhs)
{
    if(rhs._size ==0)
    {
        _size =0;
        _string =0;
    }
    _size = rhs._size;
    _string =newchar[_size +1];
    strcpy(_string, rhs._string);
}

bool MyString::operator==(constchar*sz)
{
    if(strlen(sz) != _size)
    {
        returnfalse;
    }
    return strcmp(_string, sz)?false:true;
}

bool MyString::operator==(const MyString &rhs)
{
    if(rhs._size != _size)
    {
        returnfalse;
    }
    return strcmp(_string, rhs._string)?false:true;
}

MyString& MyString::operator=(constchar*sz)
{
    if (!sz)
    {
        _size =0;
        delete[] _string; //delete current one.
        _string =0;
        return*this;
    }
    else
    {
        _size = strlen(sz);
        delete[] _string;
        _string =newchar[_size +1];
        strcpy(_string, sz);
        return*this;
    }    
}

MyString& MyString::operator=(const MyString &rhs)
{
    if (rhs._size ==0)
    {
        _size =0;
        delete[] _string;
        _string =0;
        return*this;
    }
    else
    {
        _size = rhs.size();
        delete[] _string;
        _string =newchar[_size +1];
        strcpy(_string, rhs._string);
        return*this;
    }
}
const MyString MyString::operator+(constchar*sz)
{
    MyString temp;
    temp._size = (*this)._size + strlen(sz);
    temp._string =newchar[temp._size +1];
    strcpy(temp._string, (*this)._string);
    strcat(temp._string, sz);
    return temp;
}
const MyString MyString::operator+(const MyString &rhs)
{
    MyString temp;
    temp._size = (*this)._size + rhs._size;
    temp._string =newchar[temp._size +1];
    strcpy(temp._string, (*this)._string);
    strcat(temp._string, rhs._string);
    return temp;
}

int MyString::size() const
{
    return _size;;
}

int _tmain(int argc, _TCHAR* argv[])
{
    MyString mStr1;
    MyString mStr2("MyString2");
    MyString mStr3("MyString3");
    mStr1 = mStr2 + mStr3;
    return0;
}