How to input a 2-D array by using functions in c++

Question

How to use functions for taking input from user and a function to display the 2-D array entered by the user in c++ ?
My code is below 👇but it's not working..

https://code.sololearn.com/ceuZaoiSBqZt/?ref=app

Answer 1

Mohamed ELomari in the example I gave I advised him to return the pointer that points to the first element which is,
arr or which also is same thing with arr[0][0], this way since he already knows rows, cols and the address of the first element, he can iterate thru array using this pointer. I don't see any problem here?

Answer 2

~ swim ~
why is int[row][col] illegal?

Aayushi Mittal
ever heard about vectors? using vectors, you don’t have to deal with all the array pointers crap.

Answer 3

~ swim ~
I deleted my comment that you replied to because I though it wouldn't work too...but had a go and it did. work...now I understand why.

Answer 4

~ swim ~
Actually I’ve only just read the guy’s code. Agree with you about that, wouldn’t be the case if row/col were declared as global const.

Answer 5

Martin Taylor
you mentioned that vectors are “sometimes” a viable alternative to arrays in C++.

when exactly do you prefer arrays over vectors?

Answer 6

~ swim ~
notice that the post I was referring to mentioned C++, not some low level embedded system that runs C.

also if memory is an issue, isn’t it even better to use a dynamic array?

Answer 7

~ swim ~
I did some research before posting my questions. People said the same thing, but nobody mentioned about the numerical differences between these two.

Anyway, thank you for your answers.

Answer 8

Instead of this,
return arr[rows][cols];

Change the return type of function from int to int* then,
return arr; // which is equal to &arr[0][0]

int* p = input(rows, cols);

Since you already know rows, cols and pointer to the first element, you can iterate thru array like this,

for (int i=0; i<rows; i++)
for (int j=0; j<cols; j++)
cout<< *p; // prints the element pointed by p
p++; // p now points to the next element

Answer 9

@Mustafa K., a local array cannot be directly returned from a C/C++ function as it may not exist in memory after function call is over, in simple words functions can’t return arrays in C/C++.

Answer 10

~ swim ~ oh well, I didn't know that. Does it not work even if array gets created with new operator?

Answer 11

Thank you so much for the answers!... But actually I don't know about this concept can you please elaborate..and I do not know much about pointers. Is it possible to do them without pointers ?

Answer 12

If you can insert the code or if you can give some reference regarding this problem then It'll be very helpful :-)

Answer 13

Ok thank you 👍🏻

Answer 14

~ swim ~
Well, I’ve only recently noticed that there are low embedded systems that run C++, so please excuse my ignorance.
However, since you insisted on bringing low level embedded systems into the discussion and since I have very little knowledge about it, I should ask some questions:

In what kind of systems/compilers, and shouldn’t today’s processor be so tight on memory management? Is the speed/memory difference *that* critical, that it is worth missing all the goodies stl has to offer, especially exception handling? I’ve been thinking that these differences are negligible.

Answer 15

Martin Taylor
And the question is why would you? You can declare a vector with a fixed size as well. Vectors are basically arrays under the hood, their performance are the same.

If you scrolled above, swim has pretty much addressed my question in his answers.

Answer 16

What is concord

Answer 17

Ok no problem