How to use a "vector of vector"?

Question

I already searched on the web for it but I didn't get satisfying results.

I want to create something like

vector< vector<int*> > test_vector;

How do i fill this vector of vector? How to access it's members? Maybe someone knows some nice tutorials on the web?

kind regards mikey

I would surely not use int* as the content of your vector. If you're storing numbers, just use int (or double/float/...). The use of pointers makes you have to delete each of them when your vector gets destroyed. Otherwise, you'll get a memory leak. — rubenvb, Jun 15 '10 at 17:59
See: http://stackoverflow.com/questions/823562/multi-dimensional-vector — Shog9, Jun 15 '10 at 18:06
I know your concern, but that code snippet above was only a demonstration. In effect I have to deal with pointers to objects. — Mike Dooley, Jun 15 '10 at 21:33

Ben Collins · Accepted Answer · 2010-06-15T17:58:51.153

3

Just remember that each element of test_vector is of type vector<int*>. You would fill test_vector by filling each element vector.

You can access this just like any multi-dimensional array. See:

int *p = test_vector[0][0];

Or:

int *p = test_vector.at(0).at(0);

edited Jun 15 '10 at 17:58

answered Jun 15 '10 at 17:52

Ben Collins

Thanks! I reconsidered the problem and in order I wrote some test programms which helped me in my understanding! – Mike Dooley Jun 16 '10 at 17:29

score 1 · Answer 2 · answered Jun 15 '10 at 17:51

1

answered Jun 15 '10 at 17:51

Kyra

score 1 · Answer 3 · edited Jun 15 '10 at 18:59

1

PS If you want to use some kind of a matrix, I would prefer to use only one dimensional vector and map the access (because of performance).

For example Matrix M with m rows and n columns: you can map call

M[i][j] = x to M[i*n+j] = x.

edited Jun 15 '10 at 18:59

deft_code

answered Jun 15 '10 at 17:58

LonliLokli

1

This assumes the OP wants each of the interior vectors to be the same size... which may not be the problem at hand. – andand Jun 15 '10 at 18:09
Therefore I use Matrix in my answer. – LonliLokli Jun 15 '10 at 21:24

score 1 · Answer 4 · answered Jun 15 '10 at 17:58

1

You fill a vector of vectors by putting vectors in it.

You access its members the same way you would any other vector.

answered Jun 15 '10 at 17:58

Edward Strange

4 Answers4