优先队列插入排序答案

【问题标题】：Priority queue Insertion sort优先队列插入排序
【发布时间】：2014-08-17 14:07:49
【问题描述】：

我应该使用优先队列中的链表来实现插入排序方法。我的问题是在对最后几个元素进行排序时，它会比较它们但将它们按错误的顺序排列。这是我的代码。

PQInsertionSort 类

 class PQInsertionSort
{
 Entry head;
int size;
public PQInsertionSort()
{
 head = null;
  size = 0;
}

public void insert(Entry elem) 
{

if (size == 0)
{
    System.out.println("1");

 head = elem;
}

else if(head.getKey() > elem.getKey())
{ 
    System.out.println("2");

    elem.setNext(head);
    head = elem;
}
else
{
     Entry curr;
     Entry prev;
      curr = head;
      prev = head;

    System.out.println("3");

    while(curr.getNext() != null && curr.getKey() < elem.getKey())
    {
        prev = curr;
        curr=curr.getNext();
        System.out.println("curr is "+ curr.getKey() + " elem is " +elem.getKey());

    } 

if(curr.getNext() != null)
{
     System.out.println("6");
    elem.setNext(prev.getNext());
    prev.setNext(elem);
    }
else
    {
    System.out.println("5");
    curr.setNext(elem);
    }

    }
  size++;
}

public Entry removeMin()
{
 Entry tmp = null;
 if (size == 0)
 {
   System.out.println("Queue is empty.");
 }
 else
 {
    tmp = head;
    head = head.getNext();
    size--;
 }
 if (size == 0)
 {
  head = null; 

  } 
   return tmp;
  }
public String min()
{

    return head.getName();

}

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

public boolean isEmpty()
{
return (head == null);

}

public void print()
{
 Entry p = head;
 while(p != null)
 {
     System.out.println(p.getKey() + p.getName());

     p = p.getNext();
 }

}

}

入门类

class Entry
{
  private int key;
  private String name;
  private Entry next;

  public Entry(int k, String n, Entry e)
  {
    key = k;
    name = n;

    next = e;

  }

  public void setNext(Entry e)
  {
    next = e;
  }

  public Entry getNext()
  {
    return next;
  }

  public int getKey()
  {
    return key;
  }

  public void setKey(int k)
  {
    key = k;
  }

  public String getName()
  {
    return name;
  }

  public void setName(String n)
  {
    name = n;  
  }
}

测试类

public class Test {

    public static void main(String[] args)
    {
        PQInsertionSort qs = new PQInsertionSort();

        qs.insert(new Entry(4, "Sam", null));
        qs.insert(new Entry(3, "Tim", null));
        qs.insert(new Entry(7, "Amanda", null));
        qs.insert(new Entry(1, "Chris", null));
        qs.insert(new Entry(2, "Jimbo", null));
        qs.insert(new Entry(5, "Melinda", null));
        qs.insert(new Entry(6, "Alice", null));

        qs.print();
    }

}

输出是这样的

1
2
3
prev is 4 elem is 7
5
2
3
prev is 3 elem is 2
6
3
prev is 2 elem is 5
prev is 3 elem is 5
prev is 4 elem is 5
prev is 7 elem is 5
5
3
prev is 2 elem is 6
prev is 3 elem is 6
prev is 4 elem is 6
prev is 7 elem is 6
6
1Chris
2Jimbo
3Tim
4Sam
6Alice
7Amanda
5Melinda

看看 5 是如何作为 lass elem 输出的。有什么想法吗？

【问题讨论】：

标签： java linked-list priority-queue insertion-sort

【解决方案1】：

我似乎明白了。在 while 循环之后，我不得不添加另一个条件，因为它直接传递给 else。所以应该是这样的。

if(curr.getNext() != null)
{
     System.out.println("6");
    elem.setNext(prev.getNext());
    prev.setNext(elem);

}
else if(curr.getKey() > elem.getKey())
{
    elem.setNext(prev.getNext());
    prev.setNext(elem);
}
else
    {
    System.out.println("5");

    curr.setNext(elem);
    }

}

【讨论】：