Java PriorityQueue.toString元素顺序错误
我试图在java中使用优先级最低的节点创建优先级队列。然而,我的比较器不工作,输出非常奇怪。我相信我需要改变我的比较仪,但我不知道如何改变它。 这是我的密码:Java PriorityQueue.toString元素顺序错误,java,sorting,printing,comparator,priority-queue,Java,Sorting,Printing,Comparator,Priority Queue,我试图在java中使用优先级最低的节点创建优先级队列。然而,我的比较器不工作,输出非常奇怪。我相信我需要改变我的比较仪,但我不知道如何改变它。 这是我的密码: public class HuffmanComparator implements Comparator<TreeNodeHuffman> { public int compare(TreeNodeHuffman p1, TreeNodeHuffman p2) { if (p1.frequency &l
public class HuffmanComparator implements Comparator<TreeNodeHuffman> {
public int compare(TreeNodeHuffman p1, TreeNodeHuffman p2) {
if (p1.frequency < p2.frequency) return -1;
if (p1.frequency > p2.frequency) return 1;
return 0;
}
}
public class TreeNodeHuffman {
public static void main(String[] args) {
HuffmanComparator compare = new HuffmanComparator();
TreeNodeHuffman e = new TreeNodeHuffman('e', 12702);
TreeNodeHuffman t = new TreeNodeHuffman('t', 9056);
TreeNodeHuffman a = new TreeNodeHuffman('a', 8167);
TreeNodeHuffman o = new TreeNodeHuffman('o', 7507);
TreeNodeHuffman i = new TreeNodeHuffman('i', 6966);
TreeNodeHuffman n = new TreeNodeHuffman('a', 6749);
TreeNodeHuffman s = new TreeNodeHuffman('s', 6327);
TreeNodeHuffman h = new TreeNodeHuffman('h', 6094);
TreeNodeHuffman r = new TreeNodeHuffman('r', 5987);
TreeNodeHuffman d = new TreeNodeHuffman('d', 4253);
TreeNodeHuffman l = new TreeNodeHuffman('l', 4025);
TreeNodeHuffman c = new TreeNodeHuffman('c', 2782);
TreeNodeHuffman u = new TreeNodeHuffman('u', 2758);
TreeNodeHuffman m = new TreeNodeHuffman('m', 2406);
TreeNodeHuffman w = new TreeNodeHuffman('w', 2360);
TreeNodeHuffman f = new TreeNodeHuffman('f', 2228);
TreeNodeHuffman g = new TreeNodeHuffman('g', 2015);
TreeNodeHuffman y = new TreeNodeHuffman('y', 1974);
TreeNodeHuffman p = new TreeNodeHuffman('p', 1929);
TreeNodeHuffman b = new TreeNodeHuffman('b', 1492);
TreeNodeHuffman v = new TreeNodeHuffman('v', 978);
TreeNodeHuffman k = new TreeNodeHuffman('k', 772);
TreeNodeHuffman j = new TreeNodeHuffman('j', 153);
TreeNodeHuffman x = new TreeNodeHuffman('x', 150);
TreeNodeHuffman q = new TreeNodeHuffman('q', 95);
TreeNodeHuffman z = new TreeNodeHuffman('z', 74);
PriorityQueue<TreeNodeHuffman> queue = new PriorityQueue<TreeNodeHuffman>(26, compare);
queue.add(e);
queue.add(t);
queue.add(a);
queue.add(o);
queue.add(i);
queue.add(n);
queue.add(s);
queue.add(h);
queue.add(r);
queue.add(d);
queue.add(l);
queue.add(c);
queue.add(u);
queue.add(m);
queue.add(w);
queue.add(f);
queue.add(g);
queue.add(y);
queue.add(p);
queue.add(b);
queue.add(v);
queue.add(k);
queue.add(j);
queue.add(x);
queue.add(q);
queue.add(z);
System.out.println(queue);
}
}
公共类HuffmanComparator实现Comparator{
公共整数比较(TreeNodeHuffman p1,TreeNodeHuffman p2){
if(p1.frequencyp2.频率)返回1;
返回0;
}
}
公共级TreeNodeHuffman{
公共静态void main(字符串[]args){
HuffmanComparator compare=新的HuffmanComparator();
TreeNodeHuffman e=新的TreeNodeHuffman('e',12702);
TreeNodeHuffman t=新的TreeNodeHuffman('t',9056);
TreeNodeHuffman a=新的TreeNodeHuffman('a',8167);
TreeNodeHuffman o=新的TreeNodeHuffman('o',7507);
TreeNodeHuffman i=新的TreeNodeHuffman('i',6966);
TreeNodeHuffman n=新的TreeNodeHuffman('a',6749);
TreeNodeHuffman s=新的TreeNodeHuffman('s',6327);
TreeNodeHuffman h=新的TreeNodeHuffman('h',6094);
TreeNodeHuffman r=新的TreeNodeHuffman('r',5987);
TreeNodeHuffman d=新的TreeNodeHuffman('d',4253);
TreeNodeHuffman l=新的TreeNodeHuffman('l',4025);
TreeNodeHuffman c=新的TreeNodeHuffman('c',2782);
TreeNodeHuffman u=新的TreeNodeHuffman('u',2758);
TreeNodeHuffman m=新的TreeNodeHuffman('m',2406);
TreeNodeHuffman w=新的TreeNodeHuffman('w',2360);
TreeNodeHuffman f=新的TreeNodeHuffman('f',2228);
TreeNodeHuffman g=新的TreeNodeHuffman('g',2015年);
TreeNodeHuffman y=新的TreeNodeHuffman('y',1974年);
TreeNodeHuffman p=新的TreeNodeHuffman('p',1929年);
TreeNodeHuffman b=新的TreeNodeHuffman('b',1492);
TreeNodeHuffman v=新的TreeNodeHuffman('v',978);
TreeNodeHuffman k=新的TreeNodeHuffman('k',772);
TreeNodeHuffman j=新的TreeNodeHuffman('j',153);
TreeNodeHuffman x=新的TreeNodeHuffman('x',150);
TreeNodeHuffman q=新的TreeNodeHuffman('q',95);
TreeNodeHuffman z=新的TreeNodeHuffman('z',74);
PriorityQueue=新的PriorityQueue(26,比较);
添加(e);
添加(t);
加入(a);
添加(o);
加入(i);
添加(n);
队列。添加;
添加(h);
添加(r);
添加(d);
添加(l);
添加(c);
添加(u);
添加(m);
添加(w);
添加(f);
添加(g);
添加(y);
添加(p);
加入(b);
添加(v);
添加(k);
添加(j);
添加(x);
添加(q);
添加(z);
System.out.println(队列);
}
}
结果如下:
[z,k,q,g,v,x,u,d,f,y,b,m,j,i,c,e,s,o,w,a,r,h,p,t,l,a]。
但是,输出应为[z、q、x、j、k、v、b……]。
提前谢谢 您希望较低的频率变高,因此:
public int compare(TreeNodeHuffman p1, TreeNodeHuffman p2) {
if (p1.frequency < p2.frequency) return 1;
if (p1.frequency > p2.frequency) return -1;
return 0;
}
}
public int比较(TreeNodeHuffman p1,TreeNodeHuffman p2){
如果(p1.频率p2.频率)返回-1;
返回0;
}
}
如果要测试它,请将其发送到单个线程池,并查看正在处理的作业的顺序,而不是字符串或迭代器。正如doc所说:
返回此队列中元素的迭代器。迭代器不会以任何特定顺序返回元素
可以查看快速单线程池以测试此功能。您需要逐个轮询
优先级队列中的项目toString
不会这样做
因此,不要使用System.out.println(队列)代码>执行以下操作:
while(!queue.isEmpty()) {
System.out.println(queue.poll());
}
原因是,PriorityQueue
从未在内部完全排序,请查阅堆的工作原理以了解更多详细信息。来自它的轮询项在调用期间修复了堆,因此它应该按排序的顺序输出元素。System.out.println(queue)
正在打印未排序的队列。如果要打印队列真实顺序,请遵循以下代码,该代码使用轮询从队列顶部到底部获取元素:
TreeNodeHuffman tn = null;
do{
tn = queue.poll();
if(tn!=null){
System.out.print(tn.key+",");
}
}while(tn != null);
您将看到预期的输出:
z、 q,x,j,k,v,b,p,y,g,f,w,m,u,c,l,d,r,h,s,a,i,o,a,t,e
@托马斯回答工作
我的方法是在不清空队列的情况下产生相同的结果。因此,我在PriorityQueue
上创建了一个包装器,并为它实现了next()
和hasNext()
。另外,为了精确模拟优先级队列行为,通过PriorityQueue对象扩展AbstractQueue
和委托调用提供
、查看
、轮询
和大小
等方法
priorityQueueObject.methodName()
免责声明:这需要将整个队列复制到列表中并对其进行排序
public class MyPriorityQueue<E extends Comparable<T>, T> extends AbstractQueue<E> {
Integer arrOfInts[] = { 11, 7, 15, 10, 2, 1, 4, 5, 7, 2, 18, 1, 19};
PriorityQueue<E> pq = new PriorityQueue<>();
public static void main(String[] args) {
MyPriorityQueue mpq = new MyPriorityQueue<>();
mpq.addAll(Arrays.asList(arrOfInts));
//Using iterator
Iterator it = mpq.iterator();
System.out.println("The internal priority queue:" + mpq.pq);
System.out.println("Using Iterator:");
while(it.hasNext()) {
System.out.print(it.next() + ", ");
}
System.out.println("\nUsing simple system out println:");
System.out.println(mpq);
System.out.println("Using foreach: ");
for(Object o : mpq) {
System.out.print(o + ", ");
}
}
@Override
public boolean offer(E arg0) {
return pq.offer(arg0);
}
@Override
public E peek() {
return pq.peek();
}
@Override
public E poll() {
return pq.poll();
}
@Override
public Iterator<E> iterator() {
ArrayList<E> list = new ArrayList(Arrays.asList(pq.toArray()));
Collections.sort(list, null);
return new Iterator<E>() {
@Override
public boolean hasNext() {
return !list.isEmpty();
}
@Override
public E next() {
assert (hasNext());
return list.remove(0);
}
};
}
@Override
public int size() {
return pq.size();
}
}
@LuiggiMendoza:toString
使用迭代器显示所有对象。@LuiggiMendoza从AbstractCollection的代码中看到,toString使用迭代器,因此它应该按遍历顺序打印元素。这是PriorityQueue(至少在Java 6中)使用的toString的实现。文档中说:方法迭代器()中提供的迭代器不保证以任何特定顺序遍历优先级队列的元素。
@Eran迭代器无法做到这一点,它是一个堆。如果不实际修改集合,则无法对其进行排序。如果需要一个结构,该结构将按顺序返回元素,而不改变结构,请使用树集
,而不是优先级队列
。
The internal priority queue:[1, 2, 1, 7, 5, 2, 4, 11, 7, 10, 18, 15, 19]
Using Iterator:
1, 1, 2, 2, 4, 5, 7, 7, 10, 11, 15, 18, 19,
Using simple system out println:
[1, 1, 2, 2, 4, 5, 7, 7, 10, 11, 15, 18, 19]
Using foreach:
1, 1, 2, 2, 4, 5, 7, 7, 10, 11, 15, 18, 19,