vince88 vince88 - 3 months ago 8
C++ Question

Declaring a pointer to multidimensional array and allocating the array

I've tried looking but I haven't found anything with a definitive answer. I know my problem can't be that hard. Maybe it's just that I'm tired..

Basically, I want to declare a pointer to a 2 dimensional array. I want to do it this way because eventually I will have to resize the array. I have done the following successfully with a 1D array:

int* array;
array = new int[somelength];


I would like to do the following with a 2D array but it won't compile:

int* array;
array = new int[someheight][somewidth];


The compiler gives me an error stating that ‘somewidth’ cannot appear in a constant-expression. I've tried all sorts of combinations of ** and [][] but none of them seem to work. I know this isn't that complicated...Any help is appreciated.

Answer

I just found this ancient answer still gets read, which is a shame since it's wrong. Look at the answer below with all the votes instead.


Read up on pointer syntax, you need an array of arrays. Which is the same thing as a pointer to a pointer.

int width = 5;
int height = 5;
int** arr = new int*[width];
for(int i = 0; i < width; ++i)
   arr[i] = new int[height];