Remove a column in a 2d array

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Hello, i was wondering if i freed the first line in a column if i could still access the rest of the array for example:
my array : 1,2,3,4 5,6,7,8
if i freed the 3 , could i access the last column?
thanks!

Posted 14-Jan-15 7:32am

Daniel Mashukov

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jeron1 14-Jan-15 14:22pm

Your question is confusing (at least to me). Perhaps show how you are declaring your array, and maybe describe what you mean by 'freed', and show a small 2d example.

Sergey Alexandrovich Kryukov 14-Jan-15 14:23pm

I think this is clear from the content. But yes, "freeing" depends on how memory is allocated and is generally a wrong idea. Please see Solution 1.
—SA

2 solutions

Solution 2

Your sample array doesn't look two-dimensional to me.

Generally speaking you cannot free anything unless it is a pointer to dynamic allocated memory, thus an item in a array of integers cannot be freed.
If you meant: "Could I remove an item in an array?" then the answer is "yes, you could do it" but it wouldn't be plain simple (have a look at Sergey's answer).

Posted 14-Jan-15 9:53am

CPallini

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Sergey Alexandrovich Kryukov 14-Jan-15 17:01pm

Sure, correct clarification, 5ed.
Probably, OP's "2D" is suggested by the lack of ',' after '4', so it could be understood as {{1,2,3,4}, {5,6,7,8}}... no matter. :-)
—SA

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Sergey Alexandrovich Kryukov · Accepted Answer · 2015-01-14T08:22:00

Wrong idea. Arrays are based on using of continuous memory chunks and are not suitable for removing. If want to do this, you will need to reallocate the memory and, essentially, rewrite some part of original array or all of it. This is an inefficient operation which would defeat the purpose of the array's efficiency. Therefore, you should better use some other data structure suitable for deletion, such as vector or linked list, as with the template classes vector or list found in the standard C++ library:
http://www.cplusplus.com/reference/vector/vector[^],
http://www.cplusplus.com/reference/list/list[^].

For example, "2D arrays" can be represented as vectors of vectors, lists of lists, vectors of list or lists of vectors, depending on your requirements. In fact, that will make the "jagged arrays", which would be fine for your purposes. See also: http://en.wikipedia.org/wiki/Jagged_array[^].

I also want to point out that, due the nature of C and C++ arrays, "1D array" and "2D array" is exactly the same thing. The multi-index access to the array elements is nothing but syntactic sugar: http://en.wikipedia.org/wiki/Syntactic_sugar[^].

—SA