Length of multidimensional array - c++

Question

i have a simple program for operations with matrixies, but i have a problem -> i have for example array[3][3] and i need some way how to get the number of dimensions- in this case 3, here is the code:
#include <stdio.h>
#include <stdlib.h>
int **count()
{
printf("Write number of rows and collumns in format ROWS space COLLUMNS");
int i = 0;
int j = 0;
scanf("%i %i", &i, &j);
int **mat1 = (int**)malloc(i*sizeof(int*));
for (int x = 0; x < j;x++){
mat1[x] = (int*)malloc(j*sizeof(int));
}
for (int x = 0; x < i;x++){
for (int y = 0; y < j;y++){
scanf("%i",&mat1[x][y]);
}
}
printf(Write number of rows and collumns in format ROWS space COLLUMNS");
int i2 = 0,j2 = 0;
scanf("%i %i", &i2, &j2);
int **mat2 = (int**)malloc(i2*sizeof(int*));
for (int x2 = 0; x2 < j2;x2++){
mat2[x2] = (int*)malloc(j2*sizeof(int));
}
for (int x2 = 0; x2 < i2;x2++){
for (int y2 = 0; y2 < j2;y2++){
scanf("%i",&mat2[x2][y2]);
}
}
int i3 = i, j3 = j;
int **mat3 = (int**)malloc(i3*sizeof(int*));
for (int x = 0; x < j3;x++){
mat3[x] = (int*)malloc(j3*sizeof(int));
}
for (int x3 = 0; x3 < i3;x3++){
for (int y3 = 0; y3 < j3;y3++){
mat3[x3][y3] = mat1[x3][y3] + mat2[x3][y3];
}
}
return mat3;
}
int writeMatrix(int **mat, int rows, int collumns)
{
int i = rows, j=collumns;
for (int x = 0; x < i;x++){
for (int y = 0; y < j;y++){
printf("%3i ",mat[x][y]);
}
printf("\n");
}
return 0;
}
int main()
{
int **m1 = count();
writeMatrix(m1,x,x);//HERE I NEED TO KNOW NUMBER OF ROWS AND COLLUMNS
free(m1);
}
Here is the code which worked for me in a case of normal array[][] but not in this case -
int y = (sizeof(m1)/sizeof(m1[0][0])) / (sizeof(m1)/sizeof(m1[0]));

Answer 1

You can't have a multidimensional array if you don't knwo statically the size of the first dimension, you'll need a jagged array (an array of arrays), as you did it.
And then you can still get the number of allocated rows and columns. Change the count prototype to:
int** count(int& rows, int& columns)
and in it do these assignments (after you've read the values of i and j):
rows = i;
columns = j;
And call count from main like this:
int rows;
int columns;
int** m1 = count(rows, columns);
Then you can call writeMatrix:
writeMatrix(m1, rows, columns);
BTW, unless you're doing this for educational purposes, you should use std::vector<std::vector<int>> (or some similar array class), not int**.