Question

我正在进行此AVLTree分配，我遇到了insert方法的问题。当它到达z.resetHeight（）;

时，我收到一个错误

    public void insert(K key, V value) {

    AVLnode<K, V> hold = TreeSearch(key, root);
    AVLnode<K, V> z = hold;
    DictEntry<K, V> temp = new DictEntry<K, V>(key, value);
    z.setEntry(temp);

    while (z != null) {
        z.resetHeight();
        if (java.lang.Math
                .abs(z.left().getHeight() - z.right().getHeight()) > 1) {
            z = triNodeRestructure(z.parent().parent(), z.parent(), z);
            z.left().resetHeight();
            z.right().resetHeight();
            z.resetHeight();
            break;
        }
        size++;
        z = z.parent();
    }

}

resetHeight来自AVLnode类，我不允许按照赋值中的规定进行修改。

public class AVLnode<K,V> implements Position<K,V> {
private AVLnode<K,V> parent;          // reference to the parent node
private AVLnode<K,V> left;            // reference to the left child
private AVLnode<K,V> right;           // reference to the right child
private DictEntry<K,V> entry;         // reference to the entry stored at the node
private int height;                   // height of the node for checking balance-height property

public AVLnode(DictEntry<K,V> inputEntry, AVLnode<K,V>  inputParent, AVLnode<K,V>  inputLeft, AVLnode<K,V>  inputRight)
{
    entry  = inputEntry;
    parent = inputParent;
    left   = inputLeft;
    right  = inputRight;
    height = 0;
    if (left != null ) height  = Math.max(height,1+left.getHeight());
    if (right != null ) height = Math.max(height,1+right.getHeight()); 
}

public AVLnode<K,V>  parent(){ return parent;}
public AVLnode<K,V>  left() {return left;}
public AVLnode<K,V>  right() {return right;}
public int getHeight () { return height; }
public DictEntry<K,V> getEntry() { return entry; } 
public void setParent(AVLnode<K,V>  newParent){ parent = newParent; }
public void setLeft(AVLnode<K,V>  newLeft) {left = newLeft;}
public void setRight(AVLnode<K,V>  newRight) { right = newRight; }  
public void setEntry(DictEntry<K,V> newEntry) { entry = newEntry; }
public DictEntry<K,V> element(){return entry;}

public void resetHeight() throws AVLTreeException{
if ( left == null || right == null ) throw  new AVLTreeException("Attempt to update height for external node ");
height = 1+Math.max(left.getHeight(),right.getHeight());
}

}

我认为问题在于，当我使用我的插入方法时，我还没有设置一个左或右孩子。因此getHeight会抛出异常，因为我插入的节点的两个子节点都是null。我不太确定如何实现这一点。我已经尝试创建新节点来设置为hold和左右孩子，但我不知道我应该把什么作为参数而不会弄乱列表除了null，但这只会让我回到哪里我是。

Answer 1

由于z没有任何子女，因此不能失衡，请从resetHeight()的父级开始z循环：

z.setEntry(temp);

z = z.parent();
while (z != null) {
        z.resetHeight();
        // etc...

在AVLTree中将外部节点扩展到内部节点

1 个答案: