Pointer to multidimensional array C++

Question

I am trying to understand how to use pointers with multidimensional arrays (E.g: 2 dimensions, 3 dimensions...). I saw a lot of resources online for it, but I still can't seem to understand it. The syntax is also throwing me off. What do these following syntaxes mean (Why do we need parenthesis)? What does the code do and how does it work? Thank you!

Example 1

int (*array)[5] = new int[10][5];

Example 2

int c[3][2][2]; 
int (*p)[2][2] = c;

int *array[5]; defines array as an array of five pointers to int. int (*array)[5]; defines array as a pointer to an array of five int values. — Some programmer dude
– Some programmer dude, Commented Jul 14, 2020 at 13:50
@Someprogrammerdude is right and very succinct. You can read more on this here. — Manuel
– Manuel, Commented Jul 14, 2020 at 13:53
This toy tool can be of help to fiddle for distinct meanings of types with and without parentheses: C gibberish ↔ English — Scheff's Cat
– Scheff's Cat, Commented Jul 14, 2020 at 13:59

Waqar · Accepted Answer · 2020-07-14 14:09:39Z

3

int (*arr)[5] : arr is pointer, pointing to an array of 5 ints
int (*p)[2][2] = c; : p is a pointer, pointing to an array of 2, with each row having an array of 2 ints

How does it work? Look at the following simple example:

    int (*array)[2] = new int[3][2];

    for (int i = 0; i < 3; i++)
    {
        for (int j = 0; j < 2; j++)
            array[i][j] = i + j;
    }
    
    for (int i = 0; i < 3; i++)
    {
        for (int j = 0; j < 2; j++)
            cout << array[i][j] << ' ';
        cout << '\n';
    }

Output:

0 1 
1 2 
2 3

Why do we need parenthesis?

Consider:

int *arr[3];

Here, arr is an array of size 3, which can store 3 pointers. So it is an array of pointers. See:

int a = 10;
int b = 20;
int c = 30;
arr[0] = &a; //arr[0] pointing to a
arr[1] = &b; //arr[1] pointing to b
arr[2] = &c; //arr[2] pointing to c

edited Jul 14, 2020 at 14:09

answered Jul 14, 2020 at 14:03

Waqar

9,5396 gold badges39 silver badges47 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Pointer to multidimensional array C++

1 Answer 1

Why do we need parenthesis?

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Why do we need parenthesis?

Comments

Your Answer

Sign up or log in

Post as a guest

Related