#include <iostream>
#include <string>
#include <vector>
#include <fstream>
using namespace std;

class String
{
public:
    String( ) : strLen( 0 ), bufferLen( 1 )
    { buffer = new char[ 1 ]; buffer[ 0 ] = '\0'; }

    String( const char *str )
    {
        if( str == NULL )
            str = "";

        strLen = strlen( str );
        bufferLen = strLen + 1;
        buffer = new char[ bufferLen ];
        strcpy( buffer, str );
    }

    String( const String & other )
    {
        strLen = other.strLen;
        bufferLen = strLen + 1;
        buffer = new char[ bufferLen ];
        strcpy( buffer, other.buffer );
    }

    ~String( )
    { delete [ ] buffer; }

    String operator+( const String & rhs ) const
    {
        String result = (*this);
        result += rhs;
        return result;
    }

    const String & operator+= ( const String & rhs )
    {
        if( this == &rhs )
        {
            String copy( rhs );
            return *this += copy;
        }

        int newLength = length( ) + rhs.length( );
        if( newLength >= bufferLen )
        {
            bufferLen = 2 * ( newLength + 1 );

            char *oldBuffer = buffer;
            buffer = new char[ bufferLen ];
            strcpy( buffer, oldBuffer );
            delete [ ] oldBuffer;
        }

        strcpy( buffer + length( ), rhs.buffer );
        strLen = newLength;
        return *this;
    }


    const String & operator= ( const String & rhs )
    {
        if( this != &rhs )
        {
            if( bufferLen < rhs.length( ) + 1 )
            {
                delete [ ] buffer;
                bufferLen = rhs.length( ) + 1;
                buffer = new char[ bufferLen ];
            }

            strLen = rhs.strLen;
            strcpy( buffer, rhs.buffer );
        }

        return *this;
    }

    int length( ) const
    { return strLen; }

    const char * c_str( ) const
    { return buffer; }

    char operator[]( int idx ) const
    { return buffer[ idx ]; }
    char & operator[]( int idx )
    { return buffer[ idx ]; }

    bool operator==( const String & rhs ) const
    { return strcmp( buffer, rhs.buffer ) == 0; }
    bool operator==( const char *rhs ) const
    { return strcmp( buffer, rhs ) == 0; }

private:
    char *buffer;      // storage for characters
    int bufferLen;     // size of the buffer
    int strLen;        // length of string < bufferLen
};


ostream & operator<< ( ostream & out, const String & x )
{
    out << x.c_str( );
    return out;
}

bool operator==( const char *lhs, const String & rhs )
{
    return strcmp( lhs, rhs.c_str( ) ) == 0;
}

bool operator!=( const String & lhs, const String & rhs )
{
    return strcmp( lhs.c_str( ), rhs.c_str( ) ) != 0;
}

int main( )
{
    const String s1 = "hello";
    String s2 = "world";
    String s3 = s1;

    cout << s1.length( ) << endl;
    cout << s1 << endl;
    cout << s2 << endl;
    cout << s3 << endl;

    cout << (s1==s2) << endl;
    cout << (s1!=s3) << endl;

    cout << (s1=="world") << endl;
    cout << ("world"==s1) << endl;

    for( int i = 0; i < s1.length( ); i++ )
        cout << s1[ i ] << endl;

    s3[ 0 ] = 'j';
    cout << s3 << endl;

    s3 += s2;
    cout << s3 << endl;

    return 0;
}