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MyArray.java
/*** 数组** @author* @version 2018/8/4*/
public class MyArray<E> {private E[] arr;private int size;public MyArray(int capacity){arr = (E[])new Object[capacity];size = 0;}public MyArray() {this(10);}public int getSize(){return size;}public int getCapacity(){return arr.length;}public boolean isEmpty(){return size == 0;}/*** 向数组头部插入一个元素** @param e* @return void* @author ronglexie* @version 2018/8/4*/public void addFirst(E e){add(0,e);}/*** 向数组尾部插入一个元素** @param e* @return void* @author ronglexie* @version 2018/8/4*/public void addLast(E e){add(size,e);}/*** 向数组指定位置插入一个元素** @param index* @param e* @return void* @author ronglexie* @version 2018/8/4*/public void add(int index, E e){if(index < 0 || index > size){throw new IllegalArgumentException("Add failed. Require index >= 0 and index <= size");}if(size == arr.length){
// throw new IllegalArgumentException("Add failed. Array is full.");//数组动态扩容两倍resize(2*arr.length);}for (int i= size-1; i >= index; i--){arr[i+1] = arr[i];}arr[index] = e;size++;}private void resize(int newCapacity) {E[] newData = (E[]) new Object[newCapacity];for (int i = 0; i < size; i++) {newData[i] = arr[i];}arr = newData;}/*** 获取指定位置的元素** @param index* @return E* @author ronglexie* @version 2018/8/4*/public E get(int index){if(index < 0 || index >= size){throw new IllegalArgumentException("Get failed. index is Illegal.");}return arr[index];}/*** 获取第一个元素** @param* @return E* @author ronglexie* @version 2018/8/4*/public E getFirst() {return arr[0];}/*** 获取最后一个元素** @param* @return E* @author ronglexie* @version 2018/8/4*/public E getLast() {return get(size - 1);}/*** 修改指定位置的元素** @param index* @param e* @return void* @author ronglexie* @version 2018/8/4*/public void set(int index, E e){if (index < 0 || index >= size){throw new IllegalArgumentException("Set failed. index is Illegal.");}arr[index] = e;}/*** 查看数组中是否包含某个元素** @param e* @return boolean* @author ronglexie* @version 2018/8/4*/public boolean contains(E e){for (int i = 0; i < size; i++) {if(arr[i].equals(e)){return true;}}return false;}/*** 查找元素在数组中的位置** @param e* @return int* @author ronglexie* @version 2018/8/4*/public int indexOf(E e){for (int i = 0; i < size; i++) {if(arr[i].equals(e)){return i;}}return -1;}/*** 移除数组中的一个元素** @param index* @return int* @author ronglexie* @version 2018/8/4*/public E remove(int index){if (index < 0 || index >= size){throw new IllegalArgumentException("Remove failed. index is Illegal.");}E result = arr[index];for (int i = index + 1; i < size; i++) {arr[i-1] = arr[i];}size--;//修改对象引用，垃圾回收机制回收arr[size] = null;//动态缩小数组一半容量if(size == arr.length/4 && arr.length/2 != 0){resize(arr.length/2);}return result;}/*** 移除数组中的第一个元素** @param* @return E* @author ronglexie* @version 2018/8/4*/public E removeFirst(){return remove(0);}/*** 移除数组中的最后一个元素** @param* @return int* @author ronglexie* @version 2018/8/4*/public E removeLast(){return remove(size - 1);}/*** 移除数组中的某个元素** @param e* @return void* @author ronglexie* @version 2018/8/4*/public void removeElement(E e){int index = indexOf(e);if(index != -1){remove(index);}}/*** 将索引为i和j的两个元素互相交换** @param i* @param j* @return void* @author ronglexie* @version 2018/8/19*/public void swap(int i, int j){if (i < 0 || i >= size || j < 0 || j >= size){throw new IllegalArgumentException("Swap failed. index is Illegal.");}E temp = arr[i];arr[i] = arr[j];arr[j] = temp;}/*** 自定义toString方法** @param* @return java.lang.String* @author ronglexie* @version 2018/8/4*/@Overridepublic String toString(){StringBuilder result = new StringBuilder();result.append(String.format("Array: size = %d , capacity = %d\n",size,arr.length));result.append("[");for (int i = 0; i < size; i++){result.append(arr[i]);if(i != size - 1){result.append(", ");}}result.append("]");return result.toString();}}MaxHeap.java
/*** 最大堆* 完全二叉树实现、树中的根结点都表示树中的最大元素结点** @author ronglexie* @version 2018/8/19*/
public class MaxHeap<E extends Comparable<E>> {private MyArray<E> arr;public MaxHeap(int capacity){arr = new MyArray<>(capacity);}public MaxHeap() {arr = new MyArray<>();}// 返回堆中的元素个数public int size(){return arr.getSize();}public boolean isEmpty(){return arr.isEmpty();}/*** 查找用数组实现的完全二叉树中该索引下节点的父亲节点的索引** @param index* @return int* @author ronglexie* @version 2018/8/19*/public int parent(int index){if(index == 0){throw new IllegalArgumentException("root doesn't have parent.");}return (index - 1) / 2;}/*** 查找用数组实现的完全二叉树中该索引下节点的左孩子节点的索引** @param index* @return int* @author ronglexie* @version 2018/8/19*/public int leftChild(int index){return (index * 2) + 1;}/*** 查找用数组实现的完全二叉树中该索引下节点的右孩子节点的索引** @param index* @return int* @author ronglexie* @version 2018/8/19*/public int rightChild(int index){return (index * 2) + 2;}/*** 向最大堆中添加元素** @param e* @return void* @author ronglexie* @version 2018/8/19*/public void add(E e){arr.addLast(e);shifUp(arr.getSize() - 1);}/*** 上浮节点** @param k* @return void* @author ronglexie* @version 2018/8/19*/private void shifUp(int k) {while (k > 0 && arr.get(parent(k)).compareTo(arr.get(k)) < 0){arr.swap(k,parent(k));k = parent(k);}}/*** 查找堆中最大值** @param* @return E* @author ronglexie* @version 2018/8/19*/public E findMax(){if(arr .getSize() == 0){throw new IllegalArgumentException("FindMax failed. heap is empty.");}return arr.get(0);}/*** 取出最大值** @param* @return E* @author ronglexie* @version 2018/8/20*/public E extractMax(){E result = findMax();arr.swap(0,arr.getSize() - 1);arr.removeLast();siftDown(0);return result;}/*** 下沉节点** @param k* @return void* @author ronglexie* @version 2018/8/25*/private void siftDown(int k) {while (k >= 0 && leftChild(k) < arr.getSize()){int j = leftChild(k);//找到k节点的左右子节点的最大值jif (j + 1 < arr.getSize() && arr.get(j + 1).compareTo(arr.get(j)) > 0) {j = rightChild(k);}// 运行到此，arr[j] 是 leftChild 和 rightChild 中的最大值//比较大小判断是否还需要下沉操作if(arr.get(k).compareTo(arr.get(j)) > 0){break;}arr.swap(k,j);k = j;}}}
一、非原地堆排序
HeapSort.java
import java.util.Arrays;
import java.util.Random;/*** Description: 堆排序.*/
public class HeapSort01 {final static int MAX=20; //待排序数组大小private HeapSort01(){}/*** 堆排序 * @param arr 待排序数组*/public static void heapSort(int arr[]){MaxHeap<Integer> maxHeap = new MaxHeap<>();for(int elem : arr){maxHeap.add(elem);}for(int i = arr.length - 1; i>=0; i--){arr[i] = maxHeap.extractMax();}}public static void main(String[] args) {Random random=new Random();int []arr=new int[MAX];//生成随机数测试for(int i=0;i<MAX;i++){arr[i]= random.nextInt(20);}System.out.print("待排序数组：" + Arrays.toString(arr));long start=System.currentTimeMillis();heapSort(arr);long end=System.currentTimeMillis();System.out.println("\nheapSorting time cost:"+(end-start)+"ms");for (int anArray : arr) {System.out.print(anArray + " ");}System.out.println();}
}
输出结果：
待排序数组：[12, 16, 5, 3, 0, 6, 8, 13, 7, 13, 9, 0, 1, 1, 15, 7, 4, 13, 15, 1]
heapSorting time cost:4ms
0 0 1 1 1 3 4 5 6 7 7 8 9 12 13 13 13 15 15 16
二、原地堆排序
import java.util.Arrays;
import java.util.Random;/*** Description: 堆排序. 原地排序*/
public class HeapSort02 {final static int MAX = 20; //待排序数组大小/*** 堆排序* @param arr 待排序数组*/public static void heapSort(int[] arr) {if (arr.length <= 1) {return;}int length = arr.length;// heapify：将任意数组整理成堆的形状int parent_index = (length - 2) / 2; // 最后一个叶子节点的父节点for (int i = parent_index; i >= 0; i--) {siftDown(arr, i, arr.length);}System.out.print("\nheapify后的数组：" + Arrays.toString(arr));for (int i = arr.length - 1; i >= 0; i--) {swap(arr, 0, i); // 将最大值交换到i位置siftDown(arr, 0, i);}System.out.print("\n整理后的数组：" + Arrays.toString(arr));}/*** 下沉节点：对arr[0,n) 所形成的最大堆中，索引 k 的元素，执行siftDown*/private static void siftDown(int[] arr, int k, int n) {while (leftChild(k) < n) {int j = leftChild(k); //在此轮循环中，arr[k]与arr[j]交换位置//找到k节点的左右子节点的最大值jif (j + 1 < n && arr[j + 1] > arr[j]) {j = rightChild(k);}// 运行到此，arr[j] 是 leftChild 和 rightChild 中的最大值//比较大小判断是否还需要下沉操作if (arr[k] >= arr[j]) {break;}swap(arr, k, j);k = j;}}public static void swap(int[] arr, int i, int j) {int temp = arr[i];arr[i] = arr[j];arr[j] = temp;}public static int leftChild(int index) {return (index * 2) + 1;}public static int rightChild(int index) {return (index * 2) + 2;}public static void main(String[] args) {Random random = new Random();int[] arr = new int[MAX];//生成随机数测试for (int i = 0; i < MAX; i++) {arr[i] = random.nextInt(20);}System.out.print("待排序数组：" + Arrays.toString(arr));long start = System.currentTimeMillis();heapSort(arr);long end = System.currentTimeMillis();System.out.println("\nheapSorting time cost:" + (end - start) + "ms");for (int anArray : arr) {System.out.print(anArray + " ");}System.out.println();}
}
输出结果：
待排序数组：[15, 9, 10, 12, 7, 1, 12, 18, 12, 7, 0, 8, 17, 5, 15, 3, 2, 16, 8, 14]
heapify后的数组：[18, 16, 17, 15, 14, 10, 15, 12, 12, 7, 0, 8, 1, 5, 12, 3, 2, 9, 8, 7]
整理后的数组：[0, 1, 2, 3, 5, 7, 7, 8, 8, 9, 10, 12, 12, 12, 14, 15, 15, 16, 17, 18]
heapSorting time cost:0ms
0 1 2 3 5 7 7 8 8 9 10 12 12 12 14 15 15 16 17 18 Process finished with exit code 0
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