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I want to implement the flood-fill algorithm for http://stackoverflow.com/questions/12995378/is-there-a-proper-algorithm-for-detecting-the-background-color-of-a-figure. I did it recursively, but I had a stack-overflow error. No matter - Wikipedia has a spot for a non-recursive, iterative solution.

It requires a queue. For school, we're not supposed to use Lists nor the Java Queue class (I don't even know if it does what I think it does, but it doesn't matter - I can't use it).

public class QueueOfPixeles
{
 public Pixel[] elements;
 public int numberOfElements;
 public QueueOfPixeles()
 {
 numberOfElements = 0;
 elements = new Pixel[1];
 }
 
 // Next pixel is supposed to return the last pixel element in the queue.
 // When a pixel element is returned, it will become null in the system.
 public Pixel nextPixel() {
 Pixel result = null;
 for (int i = elements.length - 1; i >= 0 && result == null; --i) {
 result = elements[i];
 if (result != null) {
 elements[i] = null;
 }
 }
 return result;
 }
 
 // Adds a new pixel to the queue.
 // Then, it checks if the capacity of the vector has been reached.
 public void add(Pixel pixel) {
 elements[numberOfElements] = pixel;
 ++numberOfElements;
 fixVector();
 }
 
 // If the vector capacity has been reached, create a new vector with all old elements
 // but with more capacity.
 private void fixVector() {
 if (numberOfElements >= elements.length) {
 Pixel[] newVector = new Pixel[(elements.length * 2) + 1];
 for (int i = 0; i < numberOfElements; ++i) {
 newVector[i] = elements[i];
 }
 elements = newVector;
 }
 }
}

WHAT IS IT SUPPOSED TO DO?

You should be able to add pixels to the end of the queue, and get the next pixel by using nextPixel(). When you retrieve the next pixel, it should be removed from the queue automatically.

DOES IT WORK?

Yes, it seems to be working. I've done a few tests and it has indeed returned all I expected.

WHAT'S THE PROBLEM?

I'd like to get some feedback about this. I can only use vectors for this project, and I feel there is something rather not-efficient with the way I manage the pixels in the queue (converting the elements to null and just that etc, or asking for more capacity size instead of using the null-spaces I made).

What do you think?