Princeton1/module8/src/main/java/com/hithomelabs/princeton1/module8/PriorityQueue.java

package com.hithomelabs.princeton1.module8;

import com.hithomelabs.princeton1.module4.Queue;
import com.hithomelabs.princeton1.module5.ComparableHelper;

import java.util.Iterator;

public class PriorityQueue<E> extends Queue<E> implements ComparableHelper {
    private int size;
    private E[] arr;
    private static final int CAPACITY = 100;
    private int capacity;

    public PriorityQueue(){
        this(CAPACITY);
    }

    public PriorityQueue(int capacity){
        arr = (E[]) new Object[capacity+1];
        this.capacity = capacity;
    }

    @Override
    public boolean isEmpty() {
        return size == 0;
    }

    @Override
    public E dequeue() {
        if(isEmpty())
            return null;
        E value = arr[1];
        ComparableHelper.exch(arr, 1, size);
        arr[size--] = null;
        Heap.sink(arr, 1, size, null, null);
        return value;
    }

    @Override
    public void enqueue(E element) {
        arr[++size] = element;
        Heap.swim(arr, size, size, null, null);
    }

    @Override
    public int size() {
        return size;
    }

    @Override
    public Iterator iterator() {
        return new Iterator() {

            int index = 1;
            @Override
            public boolean hasNext() {
                return index <= size;
            }

            @Override
            public Object next() {
                return arr[index++];
            }
        };
    }
}