I want to create enemies on the fly. Say, every time I press E, an enemy appears in a random place. Here is what I have right now.

class enemy{
      public:
      int health;
      int attack;
      int range;
      int enemyx;
      int enemyy;
      };

Right? Fairly simple, I just made a class. Everything is public right now because I'm new to classes and I don't want to have to dick around with the tangled mess that is private/protected elements.

So right now, I could, for example, have a ton of lines that go something like

enemy *enemy1;
enemy *enemy2;
etc. etc.

and then a whole "if enemy1.health = 0 then enemy1 = new enemy blah blah blah", but either I'd have to declare a LOT of enemies (not fun) or limit myself to how many enemies are on the screen at a time. Limits are good, yes, but I don't like the idea of hitting a cap and having the game crash when it tries to make one more, regardless of how high the cap is.

So how would I go about doing this? Like I said, I'm new to classes so I might not even be doing THIS right, but hey.

There's another thread currently discussing the use of standard library containers. Essentially, there are containers in the standard library of C++ that will resize themselves automatically to fit your needs (examples are those mentioned by Trent Gamblin).

One thing not mentioned in the other thread (that I recall) is object pooling. Memory allocation and deallocation are relatively expensive operations so if your enemies will be spawned and destroyed rapidly then it might be something to consider.

On the subject on "pooling" the way I like to do it is to create two vectors of pointers to objects, one vectors containing objects in use and in the other objects that aren't in use, when initializing the level or the application or what you choose to do, you can create a number of objects (pooling), and when a new enemy(or whatever) needs to be created you check if there are any objects in the unused objects vector and if there are you simply move the pointer to the used objects vector and edit it's values, if not you simply create a new object.

Some people use one vector with "flags" to check if the object is in use, I think that in general moving some values around once in a while is better than to check a value for each allocated object every time.

Mandatory flowchart that's been posted on the forums a million times (I wonder if Allegro.cc identifies duplicates of uploads and optimizes them).^[1]

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I'm just going to add a link to this post to my signature so I can easily find and link to it next time.

Hooray, according to the flowchart I should use a vector. Of course I have no goddamn clue what "need to find element by key" means.

It means key as in Key/Value. In other words, each entry has a "key" and "value" associated with it.

For example, the key might be a person's name and the value might be their age. So in effect you'd get something like the following:

map<string, int> Ages;

Ages['Nick'] = 25;
Ages['John'] = 34;
Ages['Mike'] = 17;

cout << "John is " << Ages['John'] << " years old." << endl;

Wouldn't linked lists to the job as well? I'm just curious, I find linked lists quite usefull in situations like these (I know I started using them for game objects since reading some article on gamedev.net, don't remember which one really)

Hm, ok, that clears the fog for me. I'm stuck somewhere between C and C++ actually and don't know much about STL (just some theory). I don't know how bad that is, but for now I can't say I really need something from STL that I can't handle doing myself...

Linked lists are quite easy to implement actually, I suggest trying to build an example just to have an ideea on how they work

Implementing linked-listing ability inside a class is basic (And it's educational, often the first teaching tool for pointers. I advise doing it at least once.)
Now implementing a generic container, it requires good grasp of implementing templates, and I guess it can be very obscure.