Removing an element from a char array (C)

Question

I'm trying to remove a char from an array and I'm having problems. I read how to do it with numbers but it seems is different from removing chars as it's not working for me.

If I've the following array:

char stuff[][20] = {"one", "two", "three", "four", "five"};

How can I remove the element "four" for example, so I can get

{"one", "two", "three", "five"};

How do you do it with integers? It's not that much different with strings (just remember a string is an array) — pmg
– pmg, Commented May 21, 2013 at 14:11

JeffRSon · Accepted Answer · 2013-05-21 14:10:15Z

3

You could do this by dynamically allocating all the needed memory: an array of char* as well as memory for the strings.

Then you could create another array without the item to be removed and copy all data that remains. Finally free the original array and strings.

It's a bit complex but not too hard. It may be easier if you could create a linked list - but this will probably change your application logic a bit more.

answered May 21, 2013 at 14:10

JeffRSon

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4 Comments

Avión Over a year ago

Is that hard? I mean, Isn't there a "remove" function that using the index you can remove that element?

Carl Norum Over a year ago

@Borja, nope. C programming is a lot of 'do it yourself'.

Avión Over a year ago

I see. It would be easier if I use vectors rather than array's to do this?

JeffRSon Over a year ago

Then you may use std::list - with vector you cannot remove inbetween.

unwind · Accepted Answer · 2013-05-21 14:03:23Z

2

You're going to have to copy the strings, and keep track of how many you consider to be present since the allocated space itself is not going to go away.

answered May 21, 2013 at 14:03

unwind

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Comments

John Bode · Accepted Answer · 2013-05-21 18:17:57Z

1

You can't change the size of an array in C; as declared, your stuff array will always have 5 elements (where each element is a 20-element array of char).

What you can do is copy the contents of the fifth element to the fourth element:

strcpy(stuff[3], stuff[4]); // overwrites "four" with "five"

and then empty out the fifth element:

strcpy(stuff[4], ""); // zeros out the first element in the subarray

or

memset(stuff[4], 0, sizeof stuff[4]); // zeros out entire subarray

Either way, your array will now contain the strings

{ "one", "two", "three", "five", "" }

If you really want to change the number of elements in the list (not just clear out the last one), you'll have to use a different strategy.

Problems like this usually call out for a data structure known as a linked list; each element in the list explicitly points to the next element. You can add, remove, and re-order elements in a linked list much more easily than you can in an array (even though an array can be used as the backing store). There are a number of examples (of varying quality) on the Web. However, if you can find a copy of Sedgewick's "Algorithms in C", that would be a better resource.

answered May 21, 2013 at 18:17

John Bode

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1 Comment

Avión Over a year ago

Yes, I need to change the number of elements, so the index changes as well. Thanks for the recommendation. Will try linked list.

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