数据结构Java实现——②队列-->队列的“奇葩”二 优先级队列

写在前面

应用

代码实现

package org.Stone6762.entity;

/**
* @ClassName_PriorityQData优先级队列的结点中的数据部分的描述
* @author_Stone6762
* @CreationTime_2015年1月2日 下午3:39:55
* @Description_
*/
public class PriorityQData {

/**@data该节点的数据部分
*/
private Object data;

/**@priority该结点的优先级
*/
private int priority;

/**　@Title构造器
*/
public PriorityQData(Object data, int priority) {
super();
this.data = data;
this.priority = priority;
}

public Object getData() {
return data;
}

public void setData(Object data) {
this.data = data;
}

public int getPriority() {
return priority;
}

public void setPriority(int priority) {
this.priority = priority;
}

}

package org.Stone6762.MQueue.imple;

import org.Stone6762.MQueue.MQueue;
import org.Stone6762.entity.Node;
import org.Stone6762.entity.PriorityQData;

/**
* @ClassName_PriorityQueue优先级队列
* @author_Stone6762
* @CreationTime_2015年1月2日 下午3:42:55
* @Description_
*/
public class PriorityQueue implements MQueue {

/**
* @front指向队首元素
*/
private Node front;

/**
* @rear指向队尾元素
*/
private Node rear;

/**
* @bigFront优先级队列的存储顺序_默认的是队首小
*/
private boolean bigFront;

/**
* 　@Title构造器
*/
public PriorityQueue(boolean bigFront) {
this();
this.bigFront = bigFront;
}

public PriorityQueue() {
this.front = this.rear = null;
}

@Override
public void clear() {
this.front = this.rear = null;
}

@Override
public boolean isEmpty() {

return this.front == null;
}

@Override
public int length() {
Node t = this.front;
int length = 0;
while (t != null) {
length++;
t = t.getNext();
}
return length;
}

@Override
public Object peek() {
if (front != null) {
return front.getData();
}
return null;
}

@Override
public void offer(Object data) throws Exception {

PriorityQData tData = (PriorityQData) data;
Node newNode = new Node(tData);
if (front == null) {// 对第一个元素进行特殊处理
front = rear = newNode;
} else {

// 1.根据优先级找到要插入的合适的位置
Node currNode = front, lastNode = front;

if (!bigFront) {
while (currNode != null
&& tData.getPriority() >= ((PriorityQData) currNode
.getData()).getPriority()) {
lastNode = currNode;
currNode = currNode.getNext();
}// -----------跳出循环有两种情况，一，到了队尾，二，找到了合适的位置
} else {
while (currNode != null
&& tData.getPriority() <= ((PriorityQData) currNode
.getData()).getPriority()) {
lastNode = currNode;
currNode = currNode.getNext();
}// -----------跳出循环有两种情况，一，到了队尾，二，找到了合适的位置
}

// 2.对插入的位置进行分类讨论
if (currNode == null) {// 该结点应该插在队尾
rear.setNext(newNode);
rear = newNode;
} else if (currNode == front) {// 该结点应该插在队首
newNode.setNext(front);
front = newNode;
} else {// 该结点在队中间的某一位置
newNode.setNext(currNode);
lastNode.setNext(newNode);
}
}
}

@Override
public Object poll() {

if (front != null) {
Node t = front;
front = front.getNext();
return t;
}
return null;
}

public void disPly() {
if (front != null) {
Node t = front;
while (t != null) {
PriorityQData temp = (PriorityQData) t.getData();
System.out.println("  "+temp.getData() + "       "
+ temp.getPriority());
t = t.getNext();
}
} else {
System.out.println("队列为空！！");
}
}

}