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【Java】循环队列

作者:zjq2008wd / 发布于2014/4/11/ 549

循环队列

import java.util.Iterator;

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

 private Node first;
 private Node last;
 private int N;

 private class Node {
  Item item;
  Node next;
 }

 public boolean isEmpty() {
  return first == null;
 }

 public int size() {
  return N;
 }

 public void enqueue(Item item) {
  Node oldlast = last;
  last = new Node();
  last.item = item;

  if (isEmpty()) {
   first = last;

  } else
   oldlast.next = last;
  last.next = first;
  N++;
 }

 public Item dequeue() {
  Node oldfirst = first;
  first = first.next;
  if (isEmpty())
   last = null;
  N--;
  return oldfirst.item;
 }
    public Item remove(Iterator<Item> iter) {
&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;   &nbsp;Item item = ((LoopQueueIterator) iter).current.item;
&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; &nbsp;  iter.remove();
&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;   &nbsp;return item;
&nbsp;&nbsp;   &nbsp;}
 @Override
 public Iterator<Item> iterator() {
  // TODO Auto-generated method stub
  return new LoopQueueIterator();
 }

 private class LoopQueueIterator implements Iterator<Item> {
  private Node current = first;
  private Node pre = last;

  @Override
  public boolean hasNext() {
   // TODO Auto-generated method stub
   if (isEmpty())
    return false;
   return true;
  }

  @Override
  public Item next() {
   // TODO Auto-generated method stub
   pre = current;
   current = current.next;

   return pre.item;
  }
   
  @Override
  public void remove() {
   // TODO Auto-generated method stub
   if (isEmpty())
    return;
   
   if (size() == 1) {
    first = last = current = pre = null;
    N--;
    return;
   }

   Node oldcurrent = current;
   pre.next = current.next;
   current = current.next;
   if (oldcurrent == first)
    first = current;
   if (oldcurrent == last)
    last = current;
   N--;
  }

 }

}

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