How Do I Declare A Dynamic Array And 2D Array Using Array File

Question

1.00/5 (2 votes)

See more:

Hi ^_^
we can type

C++

array <int , 10> s = {0};

to declaration a 1D array, now how do I can declare a 2D array using this way ?
on the other hand how do i can declare a dynamic array using this way (I mean what is the way to let user type the length of the array after running the program (1D and 2D array)) ?

many thanks in advance.

Posted 5-Oct-15 3:32am

Member 11801336

Add a Solution

Comments

Andreas Gieriet 5-Oct-15 15:28pm

Homework assignment? What does your text book tell about this?
Andi

Member 11801336 5-Oct-15 15:39pm

NOT HOMEWORK !
these are just questions in my mind..

Andreas Gieriet 5-Oct-15 15:41pm

No shouting please... ;-)

Member 11801336 5-Oct-15 15:46pm

I'm sorry..

Sergey Alexandrovich Kryukov 5-Oct-15 15:47pm

What have you tried so far?
—SA

2 solutions

Solution 1

The question is not really clear (see my comment to the question, by the way), but all you need to understand is this: http://www.cplusplus.com/doc/tutorial/arrays[^]. In particular, pay attention for the section "Multidimensional arrays".

Also, it's really useful to start your text file with array data with some metadata which, in particular, describes the dimensions of the array(s). This way, the code can initialize the arrays properly before reading any array data. Failure to design the file structure this way will lead to the need to read the same file twice, which of course would be nothing good.

—SA

Posted 5-Oct-15 9:52am

Sergey Alexandrovich Kryukov

Comments

Maciej Los 5-Oct-15 16:10pm

Short and to the point!
+5!

Sergey Alexandrovich Kryukov 5-Oct-15 16:47pm

Thank you, Maciej.
Look at the Andi's comment and solution though, which is better, more adequate to the question.
—SA

Andreas Gieriet 5-Oct-15 16:28pm

My 5 for the plain-old C-array description.
On the other hand, the OP asks about std::array and not plain-old C-arrays. The memory layout is identical but the initialization is weird for multidimensional std::array. See my solution #2.
Cheers
Andi

Sergey Alexandrovich Kryukov 5-Oct-15 16:45pm

I agree, thank you for the note. I did not pay attention it was about std::...
—SA

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Andreas Gieriet · Accepted Answer · 2015-10-05T10:16:00

The initialization of a multidimensional std::array is indeed a bit a surprise: you need to add an extra level of braces. E.g.

C++

#include <array>
...
using namespace std;
...
enum { OUTER = 3, INNER = 2 };

array<array<int, INNER>, OUTER> a =  { {{ 1, 2 }, { 3, 4 }, { 5, 6 }} } ;

for(size_t outer = 0; outer < OUTER; ++outer) {
	for(size_t inner = 0; inner < INNER; ++inner) {
		cout << "a[" << outer << "][" << inner << "] = " << a[outer][inner] << endl;
	}
}

Result:

a[0][0] = 1
a[0][1] = 2
a[1][0] = 3
a[1][1] = 4
a[2][0] = 5
a[2][1] = 6

You may leave away all but the outer braces and initialize the array as flat sequence of elements.

See also http://stackoverflow.com/questions/17759757/multidimensional-stdarray[^] and the referenced C++14 proposal[^] to fix that "defect".

For dynamic "arrays" you may use nested std::vectors.
Regards
Andi