一个堆的java实现

写了一个堆的java实现，既然可用数组来表示堆，为了方便，那么就用ArrayList吧。

抽象类Heap:

package com.my.test6;import java.util.ArrayList;/** * Title: 堆的抽象实现<br/> * Intention: 参考：https://my.oschina.net/BreathL/blog/71602<br/> * <p> * Class Name: com.my.test6.Heap<br/> * Create Date: 2017/7/1 23:31 <br/> * Project Name: MyTest <br/> * Company:  All Rights Reserved. <br/> * Copyright © 2017 <br/> * </p> * <p> * author: GaoWei <br/> * 1st_examiner: <br/> * 2nd_examiner: <br/> * </p> * * @version 1.0 * @since JDK 1.7 */public abstract class Heap<E extends Comparable> {private ArrayList<E> items;public Heap (ArrayList<E> items) {if (items.contains(null)) {throw new IllegalArgumentException("Element can not be null");}this.items = items;for(int i=(items.size()-1)/2;i>=0;i--){siftDown(i);}}public Heap (E[] arr) {items = new ArrayList<E>();for (int i=0;i<arr.length;i++) {if (arr[i] == null) {throw new IllegalArgumentException("Element can not be null");} else {items.add(arr[i]);}}for(int i=(items.size()-1)/2;i>=0;i--){siftDown(i);}}public Heap (){items = new ArrayList<E>();}/** * 返回左孩子下标 * @param i * @return */private int leftChildIndex(int i) {return 2*i + 1;}/** * 返回右孩子下标 * @param i * @return */private int rightChildIndex (int i) {return 2*i + 2;}/** * 返回父节点的下标 * @param i * @return */private int parentIndex (int i) {return (i - 1)/2;}/** * 返回堆的高度 * @return */public int height() {return  (int)(Math.log(items.size())/Math.log(2));}/** * 下沉操作 */public void siftDown(int i) {E e = items.get(i);int lefIndex = leftChildIndex(i);while (lefIndex < items.size()) {E selectedE = items.get(lefIndex);int selectedIndex = lefIndex;int rightIndex = lefIndex + 1;if (rightIndex < items.size()) {if (suitableThan(items.get(rightIndex), selectedE)) {selectedE = items.get(rightIndex);selectedIndex = rightIndex;}}if (suitableThan(selectedE, e)) {items.set(i, selectedE);i = selectedIndex;lefIndex = leftChildIndex(i);} else {break;}}items.set(i, e);}/** * 上浮操作 */public void siftUp(int i) {E e = items.get(i);while (i > 0) {int parentIndex = parentIndex(i);if (suitableThan(e, items.get(parentIndex))) {items.set(i, items.get(parentIndex));i = parentIndex;} else {break;}}items.set(i, e);}public abstract boolean suitableThan(E a, E b);/** * 堆尾插入元素 * @param e */public void push(E e) {if(e == null){throw new IllegalArgumentException("Element can not be null");}items.add(e);siftUp(items.size() -1);}/** * 取代堆顶元素 * @param e */public void replaceTop(E e) {if(e == null){throw new IllegalArgumentException("Element can not be null");}items.set(0, e);siftDown(0);}/** * 弹出堆顶元素 */public E pop() {if (!items.isEmpty()) {E e = items.get(0);E lastElement = items.remove(items.size()-1);if (lastElement != null && items.size() > 0){items.set(0, lastElement);siftDown(0);}return e;} else {return null;}}/** * 获得堆顶元素 */public E top(){return items.isEmpty()? null:items.get(0);}@Overridepublic String toString() {return items.toString();}}

MaxHeap:

package com.my.test6;import java.util.ArrayList;/** * Title: 大顶堆实现<br/> * Intention: <br/> * <p> * Class Name: com.my.test6.MaxHeap<br/> * Create Date: 2017/7/2 16:50 <br/> * Project Name: MyTest <br/> * Company:  All Rights Reserved. <br/> * Copyright © 2017 <br/> * </p> * <p> * author: GaoWei <br/> * 1st_examiner: <br/> * 2nd_examiner: <br/> * </p> * * @version 1.0 * @since JDK 1.7 */public class MaxHeap<E extends Comparable> extends Heap  {public MaxHeap(){}public MaxHeap(ArrayList<E> items) {super(items);}public MaxHeap(E[] arr) {super(arr);}@Overridepublic boolean suitableThan(Comparable a, Comparable b) {return a.compareTo(b) > 0;}}

MinHeap:

package com.my.test6;import java.util.ArrayList;/** * Title: 小顶堆实现<br/> * Intention: <br/> * <p> * Class Name: com.my.test6.MinHeap<br/> * Create Date: 2017/7/2 14:45 <br/> * Project Name: MyTest <br/> * Company:  All Rights Reserved. <br/> * Copyright © 2017 <br/> * </p> * <p> * author: GaoWei <br/> * 1st_examiner: <br/> * 2nd_examiner: <br/> * </p> * * @version 1.0 * @since JDK 1.7 */public class MinHeap<E extends Comparable> extends Heap {public MinHeap(){}public MinHeap(ArrayList<E> items) {super(items);}public MinHeap(E[] arr) {super(arr);}@Overridepublic boolean suitableThan(Comparable a, Comparable b) {return a.compareTo(b) < 0;}}

MyTest:

package com.my.test6;import java.util.ArrayList;import java.util.Arrays;/** * Title: <br/> * Intention: <br/> * <p> * Class Name: com.my.test6.MyTest<br/> * Create Date: 2017/7/2 16:51 <br/> * Project Name: MyTest <br/> * Company:  All Rights Reserved. <br/> * Copyright © 2017 <br/> * </p> * <p> * author: GaoWei <br/> * 1st_examiner: <br/> * 2nd_examiner: <br/> * </p> * * @version 1.0 * @since JDK 1.7 */public class MyTest {public static void main(String[] args) {MinHeap<Integer> myMinHeap = new MinHeap<Integer>();myMinHeap.push(100);myMinHeap.push(21);myMinHeap.push(3);myMinHeap.push(45);myMinHeap.push(578);myMinHeap.push(6);System.out.println("myMinHeap: "+myMinHeap);MaxHeap<Integer> myMaxHeap = new MaxHeap<Integer>();myMaxHeap.push(100);myMaxHeap.push(21);myMaxHeap.push(3);myMaxHeap.push(45);myMaxHeap.push(578);myMaxHeap.push(6);System.out.println("myMaxHeap: " + myMaxHeap);myMaxHeap.pop();System.out.println("myMaxHeap: " + myMaxHeap);System.out.println("myMaxHeap.height="+myMaxHeap.height());Heap<Integer> h3 = new MinHeap<Integer>(new ArrayList(Arrays.asList(new Integer[]{10,12,100,1,34,65,98,0})));System.out.println("h3=" + h3);System.out.println("h3.height="+h3.height());System.out.println("h3 top="+h3.top());}}

参考：

1、https://my.oschina.net/BreathL/blog/71602

2、http://blog.csdn.net/zhutulang/article/details/7746033