java - 方法 isEmpty 用于二叉树问题

Question

我正在尝试为自己编写二叉树的 isEmpty 方法，但我遇到了问题。所以这就是我正在使用的方法。

public boolean isEmpty(){
if(root == null) return true;
else return false;
}

当我只添加一个元素，然后删除该元素并调用 isEmpty 时，我得到的不是真，而是假。

我的实现有问题吗？

---

所以这是删除方法：

  /**
    * Internal method to remove from a subtree.
    * @param x the item to remove.
    * @param t the node that roots the tree.
    * @return the new root.
    * @throws ItemNotFoundException if x is not found.
    */
    protected BinaryNode<AnyType> remove( AnyType x, BinaryNode<AnyType> t )
    {
    if( t == null )
    throw new ItemNotFoundException( x.toString( ) );
    if( x.compareTo( t.element ) < 0 )
    t.left = remove( x, t.left );
    else if( x.compareTo( t.element ) > 0 )
    t.right = remove( x, t.right );
    else if( t.left != null && t.right != null ) // Two children
    {
    t.element = findMin( t.right ).element;
    t.right = removeMin( t.right );
    }
    else
    t = ( t.left != null ) ? t.left : t.right;
    return t;
    }

这是 remove 方法使用的 removeMin 方法：

        /**
         * Internal method to remove minimum item from a subtree.
         * @param t the node that roots the tree.
         * @return the new root.
         * @throws ItemNotFoundException if t is empty.
         */
         protected BinaryNode<AnyType> removeMin( BinaryNode<AnyType> t )
         {
         if( t == null )
        throw new ItemNotFoundException( );
        else if( t.left != null )
        {
        t.left = removeMin( t.left );
        return t;
        }
        else
        return t.right;
        }

Answer 1

Your remove(AnyType x, BinaryNode<AnyType> t) method searchs the node with X element and replace it by one of its children with the removeMin method (in case it has 2 children) or with the left or the right child node. Your public remove method could be something like this:

public boolean remove(AnyType x) {
    try {
        BinaryNode<AnyType> node = remove(x, root);
        if (node != null) {
            node = null;
            return true;
        }
        return fal
    } catch (Exception e) {
        //do something with the exception
        return false;
    }
}

Answer 2

检查您的删除元素代码。通常比代码找出删除节点的父节点并将相应的引用设置为空。对于最后一个元素，它必须设置为空root变量。