java如何在堆上实现heapSort？
好的，这是我最后的任务之一，当然这给我造成了最大的压力，但唯一阻止我把这个任务交进去的是能够在堆上应用heapsort，用户将他们自己的整数值输入到一个数组列表中显示，下面是代码：
heap propgram工作正常，但是Heapsort不工作，或者我不能使用它，或者在heapap类中调用它
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.NoSuchElementException;
import java.util.Scanner;
/**
*/
public class Heap<T extends Comparable<T>> {
private ArrayList<T> items;
public Heap() {
items = new ArrayList<T>();
}
private void siftUp() {
int k = items.size() - 1;
while (k > 0) {
int p = (k-1)/2;
T item = items.get(k);
T parent = items.get(p);
if (item.compareTo(parent) > 0) {
// swap
items.set(k, parent);
items.set(p, item);
// move up one level
k = p;
} else {
break;
}
}
}
public void insert(T item) {
items.add(item);
siftUp();
}
private void siftDown() {
int k = 0;
int l = 2*k+1;
while (l < items.size()) {
int max=l, r=l+1;
if (r < items.size()) { // there is a right child
if (items.get(r).compareTo(items.get(l)) > 0) {
max++;
}
}
if (items.get(k).compareTo(items.get(max)) < 0) {
// switch
T temp = items.get(k);
items.set(k, items.get(max));
items.set(max, temp);
k = max;
l = 2*k+1;
} else {
break;
}
}
}
public T delete()
throws NoSuchElementException {
if (items.size() == 0) {
throw new NoSuchElementException();
}
if (items.size() == 1) {
return items.remove(0);
}
T hold = items.get(0);
items.set(0, items.remove(items.size()-1));
siftDown();
return hold;
}
public int size() {
return items.size();
}
public boolean isEmpty() {
return items.isEmpty();
}
public String toString() {
return items.toString();
}
//----------------------------------------------------------------------------------------------------------------------------------------
public class Heapsort<T extends Comparable<T>> {
/**
* Sort the array a[0..n-1] by the heapsort algorithm.
*
* @param a the array to be sorted
* @param n the number of elements of a that have valid values
*/
public void sort(T[] a, int n) {
heapsort(a, n - 1);
}
/**
* Sort the ArrayList list by the heapsort algorithm.
* Works by converting the ArrayList to an array, sorting the
* array, and converting the result back to the ArrayList.
*
* @param list the ArrayList to be sorted
*/
public void sort(ArrayList<T> items) {
// Convert list to an array.
@SuppressWarnings("unchecked")
T[] a = (T[]) items.toArray((T[]) Array.newInstance(items.get(0).getClass(), items.size()));
sort(a, items.size()); // sort the array
// Copy the sorted array elements back into the list.
for (int i = 0; i < a.length; i++)
items.set(i, a[i]);
}
/**
* Sort the array a[0..lastLeaf] by the heapsort algorithm.
*
* @param items the array holding the heap
* @param lastLeaf the position of the last leaf in the array
*/
private void heapsort(T[] items, int lastLeaf) {
// First, turn the array a[0..lastLeaf] into a max-heap.
buildMaxHeap(items, lastLeaf);
// Once the array is a max-heap, repeatedly swap the root
// with the last leaf, putting the largest remaining element
// in the last leaf's position, declare this last leaf to no
// longer be in the heap, and then fix up the heap.
while (lastLeaf > 0) {
swap(items, 0, lastLeaf); // swap the root with the last leaf
lastLeaf--; // the last leaf is no longer in the heap
maxHeapify(items, 0, lastLeaf); // fix up what's left
}
}
/**
* Restore the max-heap property. When this method is called, the max-heap
* property holds everywhere, except possibly at node i and its children. When
* this method returns, the max-heap property holds everywhere.
*
* @param items the array holding the heap
* @param i index of the node that might violate the max-heap property
* @param lastLeaf the position of the last leaf in the array
*/
private void maxHeapify(T[] items, int i, int lastLeaf) {
int left = leftChild(i); // index of node i's left child
int right = rightChild(i); // index of node i's right child
int largest; // will hold the index of the node with the largest element
// among node i, left, and right
// Is there a left child and, if so, does the left child have an
// element larger than node i?
if (left <= lastLeaf && items[left].compareTo(items[i]) > 0)
largest = left; // yes, so the left child is the largest so far
else
largest = i; // no, so node i is the largest so far
// Is there a left child and, if so, does the right child have an
// element larger than the larger of node i and the left child?
if (right <= lastLeaf && items[right].compareTo(items[largest]) > 0)
largest = right; // yes, so the right child is the largest
// If node i holds an element larger than both the left and right
// children, then the max-heap property already held, and we need do
// nothing more. Otherwise, we need to swap node i with the larger
// of the two children, and then recurse down the heap from the larger
// child.
if (largest != i) {
swap(items, i, largest);
maxHeapify(items, largest, lastLeaf);
}
}
/**
* Form array a[0..lastLeaf] into a max-heap.
*
* @param items array to be heapified
* @param lastLeaf position of last valid data in a
*/
private void buildMaxHeap(T[] items, int lastLeaf) {
int lastNonLeaf = (lastLeaf - 1) / 2; // nodes lastNonLeaf+1 to lastLeaf are leaves
for (int j = lastNonLeaf; j >= 0; j--)
maxHeapify(items, j, lastLeaf);
}
/**
* Swap two locations i and j in array a.
*
* @param items the array
* @param i first position
* @param j second position
*/
private void swap(T[] items, int i, int j) {
T t = items[i];
items[i] = items[j];
items[j] = t;
}
/**
* Return the index of the left child of node i.
*
* @param i index of the parent node
* @return index of the left child of node i
*/
private int leftChild(int i) {
return 2 * i + 1;
}
/**
* Return the index of the right child of node i.
*
* @param i index of the parent node
* @return the index of the right child of node i
*/
private int rightChild(int i) {
return 2 * i + 2;
}
/**
* For debugging and testing, print out an array.
*
* @param a the array to print
* @param n number of elements of a to print
*/
public void printArray(T[] items, int n) {
for (int i = 0; i < n; i++)
System.out.println(items[i]);
}
}
}
import java.util.Scanner;
public class HeapApp{
/**
* @param args
*/
public static void main(String[] args) {
Heap<Integer> hp = new Heap<Integer>();
Scanner sc = new Scanner(System.in);
System.out.print("Enter next int, 'done' to stop: ");
String line = sc.next();
while (!line.equals("done")) {
hp.insert(Integer.parseInt(line));
System.out.println(hp);
System.out.print("Enter next int, 'done' to stop: ");
line = sc.next();
}
while (hp.isEmpty()) {
//int max = hp.delete();
System.out.println( " " + hp);
}
System.out.println(hp);
System.out.println("After sorting " + hp);
}
}
现在，我不是要求任何人为我做这件事，但我只是需要帮助找出如何让堆堆与堆一起工作请帮助！我尝试过的最多的方法是在Heap sort方法中设置参数
我的问题和代码不是重复的，这是基于用户输入的堆和堆：
public static void main(String[] args) {
Heap<Integer> hp = new Heap<Integer>();
Scanner sc = new Scanner(System.in);
System.out.print("Enter next int, 'done' to stop: ");
String line = sc.next();
while (!line.equals("done")) {
hp.insert(Integer.parseInt(line));
System.out.println(hp);
System.out.print("Enter next int, 'done' to stop: ");
line = sc.next();
}
另外，整个堆使用ArrayList实现：
public class Heap<T extends Comparable<T>> {
private ArrayList<T> items;
public Heap() {
items = new ArrayList<T>();
}
# 1 楼答案
向堆类中添加一个排序方法，如下所示：
然后在HeapApp类中，在打印前调用sort方法：