我正在尝试在java中实现堆。我正在测试插入。当我插入元素并在我的Heaper类中的插入方法中打印出树时，我收到的输出是
[1]
[1,16]
[16,1,1,16,4]
[16,4,1,1,16,1,4,23]
有关为何发生这种情况的任何想法？谢谢！
主要方法
public class HeapTester {
public static void main(String[] args) {
Heaper heap = new Heaper();
heap.insert(1);
heap.insert(16);
heap.insert(4);
heap.insert(23);
}}
Heaper Class
package heaptester;
import java.util.ArrayList;
public class Heaper {
private ArrayList<Integer> tree;
/**
* Constructs an empty heap
*/
public Heaper()
{
tree=new ArrayList<Integer>();
}
public boolean isEmpty()
{
if (tree.size() == 0)
{
return true;
}
return false;
}
public void insert(Integer obj)
{
if (isEmpty())
{
tree.add(obj);
System.out.println(tree);
}
else
{
int place = tree.size()-1;
int parent = (place -1)/2;
while(parent >= 0 && (tree.get(place) > tree.get(parent)))
{
swap(tree, place, parent);
place=parent;
parent = (place -1)/2;
}
tree.add(obj);
System.out.println(tree);
}
}
public Integer remove()
{
Integer root = tree.get(0);
tree.set(0 , tree.get(tree.size()-1));
System.out.println(tree);
reheapify(0);
System.out.println(tree);
return root;
}
public Integer peek()
{
return tree.get(0);
}
public int size()
{
return tree.size();
}
/**
* Swaps a parent and child elements of this heap at the specified indices
* @param place an index of the child element on this heap
* @param parent an index of the parent element on this heap
*/
private void swap(ArrayList<Integer> tree, int place, int parent)
{
Integer temp=tree.get(place);
tree.add(place, tree.get(parent));
tree.add(parent, temp);
}
/**
* Rebuilds the heap to ensure that the heap property of the tree is preserved.
* @param root the root index of the subtree to be rebuilt
*/
private void reheapify(int root)
{
if (!isLeaf(root))
{
if ( (tree.get(root) < tree.get(leftChild(root))) || (tree.get(root) < tree.get(rightChild(root))))
{
if (tree.get(leftChild(root)) > tree.get(rightChild(root)))
{
swap(tree,root, leftChild(root));
reheapify(leftChild(root));
}else
{
swap(tree,root, rightChild(root));
reheapify(rightChild(root));
}
}
}
}
private int leftChild(int pos)
{
return (2 * pos);
}
private int rightChild(int pos)
{
return (2 * pos) + 1;
}
private boolean isLeaf(int pos)
{
if (pos >= (size() / 2) && pos <= size())
{
return true;
}
return false;
}
}
答案 0 :(得分：0)
在insert方法中，您应该在获取树的大小之前将obj值添加到树中。
public void insert(Integer obj)
{
//...
else
{
tree.add(obj)
int place = tree.size()-1;
int parent = (place -1)/2;
while(parent >= 0 && (tree.get(place) > tree.get(parent)))
{
swap(tree, place, parent);
place=parent;
parent = (place -1)/2;
}
System.out.println(tree);
}