Dynamic Multi-dimensional Arrays 5

[ASingerMustDie]

Hi All

Surely this has been asked before, I would search but that particular facility appears to be permanently out-of-order.

What I am hoping to do is declare a 2-dimensional array with bounds according to two variables, such as:

int x = 50; // could be anything
iny y = 100; // could be anything
double *imageArray;

imageArray = new double [x][y];
imageArray[25][50] = 2.5;

We surely all know that this isn't quite right, but how can it be done?

Thanks in advance, and thanks for helping with my previous post

Regards.

 

[Valius]

Check this out. According to this article you really can't allocate a 2-D array, you have to do some tricks to get it to work. Hope this helps a bit:

http://cs-people.bu.edu/tflorio/teaching/assignments/maze/2Darrays.html

Niky Williams
NTS Marketing

 

[aphrodita]

You can create a 1-D array, and then to access one of the elements:
q=25;
imageArray[q*100+50];
It will grab the same element as:
imageArray[q][50];
Best Regards,

aphrodita@mail.krovatka.ru {uiuc rules}

http://www.hellforge.org

 

[mbaranski]

aphrodia's trick is a good one, I'll expand a little...

You take a long linear array and implement it as a matrix. If it's a 50 column and 100 row, and you want the 2nd col, 5th row, the formula would be:

element[5000];
/* 5th row, 2nd col is */
n = 5 * 50 + 2;
/* This moves down 5 rows, and over 2 columns. */

if you treat all of your accesses like this, you can get away with treating a 1d array as 2d. Be careful at the boundry conditions, though.

MWB

As always, I hope that helped!

Disclaimer:
Beware: Studies have shown that research causes cancer in lab rats.

 

[ASingerMustDie]

Thanks everyone.

To be frank, I never expected that it wouldn't be supported or I'd have worked on other solutions myself.

Thanks for the tips
You've all been nominated for Tipster :-D