gistfile1.txt

import edu.princeton.cs.algs4.StdRandom;

import java.util.Iterator;
import java.util.NoSuchElementException;

public class RandomizedQueue<Item> implements Iterable<Item> {

    private Item[] items;

    private int index = 0;

    public RandomizedQueue() {
        items = (Item[]) new Object[10];
    }

    public boolean isEmpty() {
        return index == 0;
    }

    public int size() {
        return index;
    }

    public void enqueue(Item item) {
        if (item == null) {
            throw new IllegalArgumentException();
        }
        if (index == items.length) {
            resize(2 * items.length);
        }
        items[index++] = item;
    }

    private void resize(int capacity) {
        Item[] copy = (Item[]) new Object[capacity];
        for (int i = 0; i < index; i++) {
            copy[i] = items[i];
        }
        items = copy;
    }

    public Item dequeue() {
        if (isEmpty()) {
            throw new NoSuchElementException();
        }
        int i = StdRandom.uniform(0, size());
        Item item = items[i];
        items[i] = null;
        index--;
        return item;
    }

    public Item sample() {
        if (isEmpty()) {
            throw new NoSuchElementException();
        }
        return items[StdRandom.uniform(0, size())];
    }

    public Iterator<Item> iterator() {
        return new RandomizedQueueIterator();
    }

    private class RandomizedQueueIterator implements Iterator<Item> {

        @Override
        public boolean hasNext() {
            return !isEmpty();
        }

        @Override
        public Item next() {
            if (!hasNext()) {
                throw new NoSuchElementException();
            }
            return dequeue();
        }

        @Override
        public void remove() {
            throw new UnsupportedOperationException();
        }
    }

}