（6）排序算法——堆排序

时间复杂度为O(n*logn)

public class HeapSort {  /** Heap sort method */  public static <E extends Comparable> void heapSort(E[] list) {    // Create a Heap of integers    Heap<E> heap = new Heap<E>();    // Add elements to the heap    for (int i = 0; i < list.length; i++)      heap.add(list[i]);    // Remove elements from the heap    for (int i = list.length - 1; i >= 0; i--)      list[i] = heap.remove();  }  /** A test method */  public static void main(String[] args) {    Integer[] list = {2, 3, 2, 5, 6, 1, -2, 3, 14, 12};    heapSort(list);    for (int i = 0; i < list.length; i++)      System.out.print(list[i] + " ");  }}class Heap<E extends Comparable> {  private java.util.ArrayList<E> list = new java.util.ArrayList<E>();  /** Create a default heap */  public Heap() {  }  /** Create a heap from an array of objects */  public Heap(E[] objects) {    for (int i = 0; i < objects.length; i++)      add(objects[i]);  }  /** Add a new object into the heap */  public void add(E newObject) {    list.add(newObject); // Append to the heap    int currentIndex = list.size() - 1; // The index of the last node    while (currentIndex > 0) {      int parentIndex = (currentIndex - 1) / 2;      // Swap if the current object is greater than its parent      if (list.get(currentIndex).compareTo(          list.get(parentIndex)) > 0) {        E temp = list.get(currentIndex);        list.set(currentIndex, list.get(parentIndex));        list.set(parentIndex, temp);      }      else        break; // the tree is a heap now      currentIndex = parentIndex;    }  }  /** Remove the root from the heap */  public E remove() {    if (list.size() == 0) return null;    E removedObject = list.get(0);    list.set(0, list.get(list.size() - 1));    list.remove(list.size() - 1);    int currentIndex = 0;    while (currentIndex < list.size()) {      int leftChildIndex = 2 * currentIndex + 1;      int rightChildIndex = 2 * currentIndex + 2;      // Find the maximum between two children      if (leftChildIndex >= list.size()) break; // The tree is a heap      int maxIndex = leftChildIndex;      if (rightChildIndex < list.size()) {        if (list.get(maxIndex).compareTo(            list.get(rightChildIndex)) < 0) {          maxIndex = rightChildIndex;        }      }      // Swap if the current node is less than the maximum      if (list.get(currentIndex).compareTo(          list.get(maxIndex)) < 0) {        E temp = list.get(maxIndex);        list.set(maxIndex, list.get(currentIndex));        list.set(currentIndex, temp);        currentIndex = maxIndex;      }      else        break; // The tree is a heap    }    return removedObject;  }  /** Get the number of nodes in the tree */  public int getSize() {    return list.size();  }}