Re: new vs. vector vs. array

From:

SG <s.gesemann@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Fri, 24 Apr 2009 02:11:09 -0700 (PDT)

Message-ID:

<e3a76a54-872d-494b-bad8-8c8e2c0eb1e0@k2g2000yql.googlegroups.com>

On 24 Apr., 10:26, "Mark S." <markstar.n0s...@hotmail.com> wrote:

Hi,
even though I'm still at the beginning of my learning process, I am
anxious to program something "real". So I would like to write a little
program to solve Sudokus with variable dimensions (n*n). I think I have
a pretty good idea about the algorithm, but since you guys here strongly
suggested to avoid new & delete as much as possible, I was wondering how
you would suggest how I store the classes:

I'd probably build a class for managing a dynamic 2D array first.
Something like this

  template<typename T>
  class vector2d
  {
    std::vector<T> elements;
    //...
  public:
    array2d(int rows, int cols, T const& fill = T());

    int rows() const;
    int cols() const;

    T const& operator()(int r, int c) const;
    T & operator()(int r, int c);
  };

The problem is that I don't know how to deal with multidimensional
vectors or arrays. I was thinking of using a single vector which is n*n
big. Of course, I would have to convert the numbers then (eg. for 3*3,
[1][1] would become [3]). Moreover, this solution does not seem very
elegant to me.

Why not?

So, what would you recommend?
An array of pointers to the elements?

No. I would not recommend that. You'd need to explicitly provide a
destructor for cleaning up which also implies the need for user-
defined or explicitly disabled copy and assignment operations (see C++
"rule of three").

A vector of pointers?

No. I would not recommend that for the same reasons as above.

Cheers!
SG