How to declare a multidimensional array using new

Question

How do I declare a multidimensional array using new ? A normal array would look like this:

int* ponteiro = new int[5];

But

int* ponteiro = new int[5][5];

does not compile ! but

int array[5][5];

works perfectly.

Answer 1

The best way to declare the array multidimensional is to declare an array of pointers for each level and initialize the level within a looping.

Example for ponteiro[30][100]:

// Declara e cria o primeiro nível como ponteiro duplo de 30 elementos
int **ponteiro = new int*[30];

// Para cada item, cria um vetor de 100 elementos
for(int i=0; i<30; i++)
    ponteiro[i] = new int[100];

And the code to dislocate the array:

// Desaloca cada um dos items
for(int i=0; i<30; i++)
    delete ponteiro[i];

// Desaloca a variável ponteiro
delete ponteiro;

To arrays with a variable dimension, it is possible to use the syntax:

int (*ponteiro)[100] = new int[30][100];

And if you are compiling the program to the c++2011 standard (or higher), you can directly initialize the internal arrays within an extended list with the syntax (example for [3][2]):

int **ponteiro = new int*[3]{ new int[2], new int[2], new int[2] };

Regardless of the form of statement, it is important to always remember to shift memory with delete.