I want to be able to create a 2d array the size of the width and height I read from a file, but I get errors when I say:
int array[0][0]
array = new int[width][height]
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See stackoverflow.com/questions/5279643/…Zan Lynx– Zan Lynx2011-04-01 01:42:39 +00:00Commented Apr 1, 2011 at 1:42
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related FAQfredoverflow– fredoverflow2011-04-01 06:12:44 +00:00Commented Apr 1, 2011 at 6:12
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Use a std::vector.Jesper Juhl– Jesper Juhl2022-10-23 09:30:44 +00:00Commented Oct 23, 2022 at 9:30
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3 Answers
You should use pointer to pointers :
int** array;
array = new int*[width];
for (int i = 0;i<width;i++)
array[i] = new int[height];
and when you finish using it or you want to resize, you should free the allocated memory like this :
for (int i = 0;i<width;i++)
delete[] array[i];
delete[] array;
To understand and be able to read more complex types, this link may be useful :
http://www.unixwiz.net/techtips/reading-cdecl.html
Hope that's Helpful.
If the array is rectangular, as in your example, you can do it with just one allocation:
int* array = new int[width * height];
This effectively flattens the array into a single dimension, and it's much faster.
Of course, this being C++, why don't you use std::vector<std::vector<int> >?
Comments
Try this way:
int **array; // array is a pointer-to-pointer-to-int
array = malloc(height * sizeof(int *));
if(array == NULL)
{
fprintf(stderr, "out of memory\n");
exit or return
}
for(i = 0; i < height ; i++)
{
array[i] = malloc(width * sizeof(int));
if(array[i] == NULL)
{
fprintf(stderr, "out of memory\n");
exit or return
}
}
array = new int*[width];
if(array == NULL)
{
fprintf(stderr, "out of memory\n");
exit or return
}
else
{
for (int i = 0;i<width;i++)
array[i] = new int[height];
}
