Initializing multidimensional dynamical array in c++ - c++

Question

I'm having problems declaring a multidimensional dynamical array in c style. I want to declare dynamically an array like permutazioni[variable][2][10], the code i'm using is as following (carte is a class i defined):
#include "carte.h"
//other code that works
int valide;
carte *** permutazioni=new carte**[valide];
for (int i=0; i<valide; i++){
permutazioni[i]=new carte*[2];
for (int j=0; j<2; j++) permutazioni[i][j]=new carte[10];
}
the problem is, whenever i take valide=2 or less than 2, the code just stops inside the last for (int i=0; i<valide; i++) iteration, but if i take valide=3 it runs clear without any problem. There's no problem as well if i declare the array permutazioni[variable][10][2] with the same code and any value of valide. I really have no clue on what the problem could be and why it works differently when using the two different 3d array i mentioned before

Answer 1

You show a 3D array declared as permutazioni[variable][10][2] but when you tried to dynamical allocate that you switched the last two dimensions.
You can do something like this:
#include <iostream>
#define NVAL 3
#define DIM_2 10 // use some more meaningfull name
#define DIM_3 2
// assuming something like
struct Card {
int suit;
int val;
};
int main() {
// You are comparing a 3D array declared like this:
Card permutations[NVAL][DIM_2][DIM_3];
// with a dynamical allocated one
int valid = NVAL;
Card ***perm = new Card**[valid];
// congrats, you are a 3 star programmer and you are about to become a 4...
for ( int i = 0; i < valid; i++ ){
perm[i] = new Card*[DIM_2];
// you inverted this ^^^ dimension with the inner one
for (int j = 0; j < DIM_2; j++)
// same value ^^^^^
perm[i][j] = new Card[DIM_3];
// inner dimension ^^^^^
}
// don't forget to initialize the data and to delete them
return 0;
}
A live example here.
Apart from that it is always a good idea to check the boundaries of the inddecs used to access to the elements of the array.

Answer 2

How about using this syntax? Haven't tested fully with 3 dimensional arrays, but I usually use this style for 2 dimensional arrays.
int variable = 30;
int (*three_dimension_array)[2][10] = new int[variable][2][10];
for(int c = 0; c < variable; c++) {
for(int x = 0; x < 2; x++) {
for(int i = 0; i < 10; i++) {
three_dimension_array[c][x][i] = i * x * c;
}
}
}
delete [] three_dimension_array;
Obviously this could be c++ 11/14 improved. Could be worth a shot.