CODEWITHSUNDEEP
carraysresizesizearraylist
Aaron de Windt
Aaron de Windt

Reputation: 17708

How can I change the size of an array in C?

I am experimenting a little bit with gamestudio. I am now making a shooter game. I have an array with the pointers to the enemies. When an enemy is killed, I want to remove him from the list. And I also want to be able to create new enemies.

Gamestudio uses a scripting language named lite-C. It has the same syntax as C and on the website they say, that it can be compiled with any C compiler. It is pure C, no C++ or anything else.

I am new to C. I normally program in .NET languages and some scripting languages.

Upvotes: 22

Views: 118622

Answers (6)

Ev0lv3zz
Ev0lv3zz

Reputation: 58

I wanted to lower the array size, but didn't worked like:

myArray = new int[10];//Or so.

So I've tried creating a new one, with the size based on a saved count.

int count = 0;

for (int i = 0; i < sizeof(array1)/sizeof(array1[0]); i++){
  if (array1[i] > 0) count++;
}

int positives[count];

And then re-pass the elements in the first array to add them in the new one.

//Create the new array element reference.

int x = 0;

for (int i = 0; i < sizeof(array1)/sizeof(array1[0]); i++){
  if (array1[i] > 0){ positives[x] = array1[i]; x++; }
}

And here we have a brand new array with the exact number of elements that we want (in my case).

Upvotes: 0

dan04
dan04

Reputation: 90995

You can't. This is normally done with dynamic memory allocation.

// Like "ENEMY enemies[100]", but from the heap
ENEMY* enemies = malloc(100 * sizeof(ENEMY));
if (!enemies) { error handling }

// You can index pointers just like arrays.
enemies[0] = CreateEnemy();

// Make the array bigger
ENEMY* more_enemies = realloc(enemies, 200 * sizeof(ENEMY));
if (!more_enemies) { error handling }
enemies = more_enemies;

// Clean up when you're done.
free(enemies);

Upvotes: 41

Matthieu
Matthieu

Reputation: 16397

As NickTFried suggested, Linked List is one way to go. Another one is to have a table big enough to hold the maximum number of items you'll ever have and manage that (which ones are valid or not, how many enemies currently in the list).

As far as resizing, you'd have to use a pointer instead of a table and you could reallocate, copy over and so on... definitely not something you want to do in a game.

If performance is an issue (and I am guessing it is), the table properly allocated is probably what I would use.

Upvotes: 1

user173424
user173424

Reputation:

Arrays are static so you won't be able to change it's size.You'll need to create the linked list data structure. The list can grow and shrink on demand.

Upvotes: 3

dj2
dj2

Reputation: 9618

Take a look at realloc which will allow you to resize the memory pointed to by a given pointer (which, in C, arrays are pointers).

Upvotes: 1

user180825
user180825

Reputation:

Once an array in C has been created, it is set. You need a dynamic data structure like a Linked List or an ArrayList

Upvotes: 3

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