题目：如下为类型 CMyString 的声明，请为该类型添加赋值运算符函数

class CMyString
{
public:
    CMyString( char * pData = NULL );
    CMyString( const CMyString & str );
    ~CMyString( void );
private:
    char * m_pData;
};

CMyString & CMyString::operator = ( const CMyString & str )
{
    if( this == &str )
        return *this;

    delete []m_pData;
    m_pData = NULL;
    m_pData = new char[ strlen( str.m_pData ) + 1 ];
    strcpy( m_pData, str.m_pData );
    return *this;
}

CMyString & CMyString::operator = ( const CMyString & str )
{
    if( this != &str )
    {
        CMyString strTemp( str );

        char * pTemp = strTemp.m_pData;
        strTemp.m_pData = m_pData;
        m_pData = pTemp;
    }

    return *this;
}