java使用堆结构实现优先队列

来源：互联网发布：深度linux桌面编辑：程序博客网时间：2024/05/20 18:19
package com.structures.tree;import java.util.NoSuchElementException;/* * 小顶堆 java使用堆结构实现优先队列 * http://www.oschina.net/code/snippet_855019_15069 */public class JPriorityQueue<E> {class QueueNode<E> {int capacity;int size;E[] queue;QueueNode(int capacity) {this.capacity = capacity;}}QueueNode<E> node;public void print(){E[] objs=this.node.queue;for(int i=0;i<this.node.size;i++){System.out.print(objs[i]+"  ");}System.out.println();}public JPriorityQueue(int capacity) {node = new QueueNode<E>(capacity);node.size = 0;node.queue = (E[]) new Object[capacity + 1];}public void add(E x) {int k = node.size;while (k > 0) {int parent = (k - 1) / 2;E data = node.queue[parent];Comparable<E> key = (Comparable) x;if (key.compareTo(data) >= 0)break;node.queue[k] = data;k = parent;}node.queue[k] = x;node.size++;}public E remove() {int parent = 0;if (node.size == 0) {throw new NoSuchElementException("queue is null");}E min = node.queue[0];// topE last = node.queue[node.size - 1];// lastnode.queue[0] = last;// add the last to topnode.queue[node.size - 1] = null;node.size--;Comparable<? super E> complast = (Comparable<? super E>) last;if (node.size == 2 && complast.compareTo(node.queue[1]) > 0) { // 只剩下最后两个结点，进行比较node.queue[0] = node.queue[1];node.queue[1] = last;}if (node.size > 2) { // 大于三个结点的，向下旋转while (parent < node.size / 2) {int left = 2 * parent + 1;// left childint right = left + 1;// right childE root = node.queue[parent];Comparable<? super E> comproot = (Comparable<? super E>) root;if (comproot.compareTo(node.queue[left]) < 0&& comproot.compareTo(node.queue[right]) < 0)break;Comparable<? super E> compleft = (Comparable<? super E>) node.queue[left];if (compleft.compareTo(node.queue[right]) <= 0) {node.queue[parent] = node.queue[left];node.queue[left] = root;parent = left;} else {node.queue[parent] = node.queue[right];node.queue[right] = root;parent = right;}if (right * 2 >= node.size)break;}}return min;}public static void main(String[] args) {JPriorityQueue<String> queue = new JPriorityQueue<String>(10);queue.add("Z");queue.add("B");queue.add("QZA");queue.add("QBA");queue.add("EAA");queue.add("A");queue.print();// queue.remove();// queue.remove();// queue.remove();// queue.remove();// queue.remove();System.out.println(queue.remove());System.out.println(queue.remove());System.out.println(queue.remove());System.out.println(queue.remove());System.out.println(queue.remove());System.out.println(queue.remove());}}
0 0