multidmensional dynamic array

Hello

I need a 2-dimensional dynamic bool array with 2 fixed columns and dynamic number of rows.

Code:

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bool *name[2];
name = new bool..?

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What would be the proper way of implementing it?

Thanks a lot for help!

Apart from all the weird specialization stuff, what's wrong with vector< vector<bool> >?

Or vector<bool> name_col1, vector<bool> name_col2. Or vector<bool> name[2]?

Because I'm not allowed to use vector.

Do you ever have to resize? Or can you just say new bool[some_number][2] and be done with it?

Can you use std::pair? Then you could use a normal dynamic array of pairs.

I didn't realize at first you wanted fixed size columns instead of rows. I don't know the proper syntax off the top of my head. My guess is that it involves strategically placed parentheses.

Edit: tabstop's idea is probably best.

Isn't it just this?

Code:

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name[0] = new bool[ m ];
name[1] = new bool[ n ];

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(m and n are arbitrary)

What is wrong with using bool *name = new bool[ width * height]?

I dont have to resize it once its allocated.

Oh ok. Well how about this then:

Example:

Code:

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bool *name = new bool[width * height];

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I dunno if anyone had suggested that before, but it sounds good to me.

This will give me an error:

Code:

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bool **arr;
arr= new bool[x][2];

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Quote:

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Originally Posted by master5001

Oh ok. Well how about this then:

Example:

Code:

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bool *name = new bool[width * height];

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I dunno if anyone had suggested that before, but it sounds good to me.

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Should that really work?

Code:

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bool** name = new bool*[2];

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and then dynamically allocate the rows (name[][0] and name[][1]).

Yep :) Behold!

Example:

Code:

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#include <iostream>

#define WIDTH 5
#define WIDTH 5

inline
bool &getValue(bool *name, size_t x, size_t y)
{
  return name[y*WIDTH + x];
}

int main(void)
{
  bool *name = new bool[WIDTH * HEIGHT];

  // do stuff..

  std::cout << getValue(name, 3, 4) << std::endl;

  return 0;
}

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Quote:

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Originally Posted by l2u

This will give me an error:

Code:

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bool **arr;
arr= new bool[x][2];

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---

The return of new bool[x][2] is not of type bool **, but of type bool (*)[2]; that is, a pointer to a bool[2].

I need that twodimensional bool array to write in all possible combinations of 0 and 1 without repeating.

So if I have a variable x = 3 (which means number of cells)

There are 3^2 (8) possible combinations.

Now the array should look like:

Code:

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0: 0 0 0
1: 0 0 1
2: 0 1 0
3: 0 1 1
4: 1 0 0
5: 1 0 1
6: 1 1 0
7: 1 1 1

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Any help on implementing this would be highly appreciated!

If I were given so many arbitrary restrictions like you have in your assignment. I would write my own custom container class. But I guess I am full of crazy ideas like that---or perhaps I understand that the whole objective of the assignment is to get you to realize that is the best option.

I'm probably being stupid, but why do you need a 2D array for this?

I also think that tabstop has given the answer. Use bool (*table)[2] = new bool [somenumber][2]

Or just use a fixed size array if you can be reasonably sure that x isn't going to be enormous - there is no great difference in how much memory you can allocate for a dynamic array or a fixed array, and until you actually USE the mmemoy in a fixed array, it won't actually use up (much) RAM in your machine.

--
Mats

Quote:

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Originally Posted by l2u

I need that twodimensional bool array to write in all possible combinations of 0 and 1 without repeating.

So if I have a variable x = 3 (which means number of cells)

There are 3^2 (8) possible combinations.

Now the array should look like:

Code:

---

0: 0 0 0
1: 0 0 1
2: 0 1 0
3: 0 1 1
4: 1 0 0
5: 1 0 1
6: 1 1 0
7: 1 1 1

---

Any help on implementing this would be highly appreciated!

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This is not a two-dimensional array with exactly two columns. This is a two-dimensional array where the columns (n) and rows (2**n) are both dynamic. Is it a requirement to use a two-dimensional array to solve this problem? It's pretty easy to get from 7 to 1 1 1 without it.

Quote:

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I also think that tabstop has given the answer. Use bool (*table)[2] = new bool [somenumber][2]

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You can make this prettier with a well-placed typedef.

Code:

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typedef bool (*TwoBools)[2];
TwoBools *table = new TwoBools[somenumber]

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