Re: new vs. vector vs. array

From:
James Kanze <james.kanze@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Sat, 25 Apr 2009 01:36:36 -0700 (PDT)
Message-ID:
<1f5a7627-1951-488b-8302-2498effbf849@x3g2000yqa.googlegroups.com>
On Apr 24, 11:11 am, SG <s.gesem...@gmail.com> wrote:

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

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);
  };


He doesn't really need a template for the moment. Since he's
still at the beginning of his learning process, a simple
implementation of Vector2dOfInt should suffice. (For that
matter, the preferred method of developing this sort of template
is first to get a non-template version working, then templatize
it.)

On the other hand, I'm wondering about his data representation
to begin with. My Sudoku solver didn't use any two dimensional
arrays of any sort.

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?


Again, I think he's gotten it backwards. Standard Sudoku
consists of a set of 81 squares. Each square is in three
different subsets. The traditional layout speaks of rows,
columns and I don't know what they call the third, but that's
really irrelevant with regards to solving the problem.

--
James Kanze (GABI Software) email:james.kanze@gmail.com
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