Dynamic memory allocation for 3D array [duplicate]

Question

Possible Duplicates:
Malloc a 3-Dimensional array in C?
dynamic allocation/deallocation of 2D & 3D arrays

How can i allocate 3D arrays using malloc?

Answer 1

There are two different ways to allocate a 3D array. You can allocate it either as a 1D array of pointers to a (1D array of pointers to a 1D array). This can be done as follows:

 int dim1, dim2, dim3;
 int i,j,k;
 double *** array = (double ***)malloc(dim1*sizeof(double**));

        for (i = 0; i< dim1; i++) {

         array[i] = (double **) malloc(dim2*sizeof(double *));

          for (j = 0; j < dim2; j++) {

              array[i][j] = (double *)malloc(dim3*sizeof(double));
          }

        }

Sometimes it is more appropriate to allocate the array as a contiguous chunk. You'll find that many existing libraries might require the array to exist in allocated memory. The disadvantage of this is that if your array is very very big you might not have such a large contiguous chunk available in memory.

const int dim1, dim2, dim3;  /* Global variables, dimension*/

#define ARR(i,j,k) (array[dim2*dim3*i + dim3*j + k])
double * array = (double *)malloc(dim1*dim2*dim3*sizeof(double));

To access your array you just use the macro:

ARR(1,0,3) = 4;

Answer 2

This would work

int main()
{

    int ***p,i,j;

    p=(int ***) malloc(MAXX * sizeof(int **));

    for(i=0;i<MAXX;i++)
    {
        p[i]=(int **)malloc(MAXY * sizeof(int *));
        for(j=0;j<MAXY;j++)
            p[i][j]=(int *)malloc(MAXZ * sizeof(int));
    }

    for(k=0;k<MAXZ;k++)
        for(i=0;i<MAXX;i++)
            for(j=0;j<MAXY;j++)
                p[i][j][k]=<something>;
}

Answer 3

array = malloc(num_elem * num_elem * num_elem * sizeof(array_elem));

Why not? :)