enum
{
    white,
    gray,
    black,
};

bool is_cyclic_rec( int v, const int * const *neighs, char *vis )
{
    if ( vis[ v ] == black )
        return false;
    if ( vis[ v ] == gray )
        return true;

    vis[ v ] = gray;

    for( const int *succ = neighs[ v ]; *succ >= 0; ++ succ )
        if ( is_cyclic_rec( *succ, neighs, vis ) )
            return true;

    vis[ v ] = black;
    return false;
}

bool is_cyclic( const int * const *neighs, char *scratch )
{
    for ( int v = 0; neighs[ v ]; ++ v )
        scratch[ v ] = white;

    for ( int v = 0; neighs[ v ]; ++ v )
    {
        if ( is_cyclic_rec( v, neighs, scratch ) )
            return true;
    }

    return false;
}