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package algs13;
import stdlib.*;
import java.util.Iterator;
import java.util.NoSuchElementException;
/* ***********************************************************************
 *  Compilation:  javac ResizingArrayQueue.java
 *  Execution:    java ResizingArrayQueue < input.txt
 *  Data files:   http://algs4.cs.princeton.edu/13stacks/tobe.txt
 *
 *  Queue implementation with a resizing array.
 *
 *  % java ResizingArrayQueue < tobe.txt
 *  to be or not to be (2 left on queue)
 *
 *************************************************************************/

public class XResizingArrayQueue<T> implements Iterable<T> {
  private T[] q; // queue elements
  private int N = 0; // number of elements on queue
  private int first = 0; // index of first element of queue
  private int last = 0; // index of next available slot

  // cast needed since no generic array creation in Java
  @SuppressWarnings("unchecked")
  public XResizingArrayQueue () {
    q = (T[]) new Object[2];
  }

  public boolean isEmpty () { return N == 0; }
  public int size () { return N; }

  private void resize (int capacity) {
    if (capacity <= N) throw new IllegalArgumentException ();
    @SuppressWarnings("unchecked")
    T[] temp = (T[]) new Object[capacity];
    for (int i = 0; i < N; i++)
      temp[i] = q[(first + i) % q.length];
    q = temp;
    first = 0;
    last = N;
  }

  public void enqueue (T item) {
    if (N == q.length) resize (2 * q.length); // double size of array if necessary
    q[last] = item; // add item
    last = (last + 1) % q.length;
    N++;
  }

  // remove the least recently added item
  public T dequeue () {
    if (isEmpty ()) throw new Error ("Queue underflow");
    T item = q[first];
    q[first] = null; // to avoid loitering
    N--;
    first = (first + 1) % q.length;
    if (N > 0 && N == q.length / 4) resize (q.length / 2); // shrink size of array if necessary
    return item;
  }

  public Iterator<T> iterator () { return new QueueIterator (); }
  private class QueueIterator implements Iterator<T> {
    private int i = 0;
    public boolean hasNext () { return i < N; }
    public void remove () { throw new UnsupportedOperationException (); }
    public T next () {
      if (!hasNext ()) throw new NoSuchElementException ();
      T item = q[(first + i) % q.length];
      i++;
      return item;
    }
  }

  // A test client
  public static void mainx (String[] args) {
    XResizingArrayQueue<String> q = new XResizingArrayQueue<> ();
    while (!StdIn.isEmpty ()) {
      String item = StdIn.readString ();
      if (!item.equals ("-")) q.enqueue (item);
      else StdOut.print (q.dequeue () + " ");
    }
    StdOut.println ("(" + q.size () + " left on queue)");
  }

  public String toString () {
    if (isEmpty ()) return "[]";
    StringBuilder sb = new StringBuilder ("[");
    Iterator<T> i = iterator ();
    sb.append (i.next ());
    while (i.hasNext ()) {
      sb.append (" ");
      sb.append (i.next ());
    }
    sb.append ("]");
    return sb.toString ();
  }
  private void check (String expected) {
    if (N < 0 || N > q.length) throw new Error ();
    if (N == 0 && q.length != 2) throw new Error ("Expected length 2, got " + q.length);
    if (N != 0 && N < q.length / 4) throw new Error ();
    if (((first + N) % q.length) != last) throw new Error ();
    for (int i = 0; i < N; i++) {
      if (q[(first + i) % q.length] == null) throw new Error ();
    }
    for (int i = N; i < q.length; i++) {
      if (q[(first + i) % q.length] != null) throw new Error ();
    }
    if (expected != null) {
      if (!expected.equals (this.toString ())) throw new Error ("Expected \"" + expected + "\", got \"" + this
          + "\"");
    }
    StdOut.println (this);
  }
  private void check (T iExpected, T iActual, String expected) {
    if (!iExpected.equals (iActual)) throw new Error ("Expected \"" + iExpected + "\", got \"" + iActual + "\"");
    check (expected);
  }
  public static void main (String args[]) {
    XResizingArrayQueue<Integer> d1;
    Integer k;
    d1 = new XResizingArrayQueue<> ();
    d1.enqueue (11);
    d1.check ("[11]");
    d1.enqueue (12);
    d1.check ("[11 12]");
    k = d1.dequeue ();
    d1.check (11, k, "[12]");
    k = d1.dequeue ();
    d1.check (12, k, "[]");

    d1 = new XResizingArrayQueue<> ();
    for (int i = 10; i < 20; i++)
      d1.enqueue (i);
    d1.check ("[10 11 12 13 14 15 16 17 18 19]");

    for (int i = 0; i < 10; i++) {
      d1.dequeue ();
      d1.check (null);
    }
    try {
      d1.dequeue ();
      throw new Error ("Expected exception");
    } catch (Error e) {}
  }
}