Question

我实现了递归算法来删除BST中的节点，但是如果要删除的节点有两个子节点，它似乎无法正常工作。以下是用于删除节点的方法的代码：

public boolean delete(int val)
{


    Node nodeToBeDeleted = find(val);
    if(nodeToBeDeleted != null)
    {
        //case 1: node has no children
        if(nodeToBeDeleted.leftChild == null && nodeToBeDeleted.rightChild == null)
            deleteCase1(nodeToBeDeleted);

        //case 3: node has two children
        else if(nodeToBeDeleted.leftChild != null && nodeToBeDeleted.rightChild != null)
        {
            deleteCase3(nodeToBeDeleted);
        }

        //case 2: node has one child
        else if(nodeToBeDeleted.leftChild != null)
        {
            //case 2 where left child should be deleted
            deleteCase2(nodeToBeDeleted);
        }

        else if(nodeToBeDeleted.rightChild != null)
        {
            //case 2 where right child should be deleted
            deleteCase2(nodeToBeDeleted);
        }

        return true;
    }
    else
        return false;
}

这里有deleteCase1，deleteCase2和deleteCase3方法：

private void deleteCase1(Node nodeToBeDeleted)
{
        //check if node to be deleted is a left or a right child of the parent of the node to be deleted
        if(nodeToBeDeleted.parent.leftChild == nodeToBeDeleted)
        {
            nodeToBeDeleted.parent.leftChild = null;
        }
        else if(nodeToBeDeleted.parent.rightChild == nodeToBeDeleted)
        {
            nodeToBeDeleted.parent.rightChild = null;
        }
}

这里找到方法：

public Node find(int val)
{
    if(root != null)
    {
        return findNode(root, new Node(val));
    }

    return null;
}

private Node findNode(Node search, Node node)
{
    if(search == null)
        return null;

    if(search.data == node.data)
    {
        return search;
    }
    else
    {
        Node returnNode = findNode(search.leftChild, node);

        if(returnNode == null)
        {
            returnNode = findNode(search.rightChild, node);
        }

        return returnNode;
    }
}

minLeftTreversal方法：

private Node minLeftTreversal(Node node)
{
    if(node.leftChild == null)
        return node;

    return minLeftTreversal(node.leftChild);
}

树的结构如下所示： enter image description here

算法可以正常工作，如果我删除75，但如果我尝试删除25，它就会混乱。

提前谢谢！

Answer 1

public boolean delete(int val)中的第一个if语句缺少{和}

        //case 1: node has no children
        if(nodeToBeDeleted.leftChild == null && nodeToBeDeleted.rightChild == null)
        { // <---- ADD THIS
            deleteCase1(nodeToBeDeleted);
        } // <---- AND ADD THIS
        //case 3: node has two children
        else if(nodeToBeDeleted.leftChild != null && nodeToBeDeleted.rightChild != null)
        {
            deleteCase3(nodeToBeDeleted);
        }

BST：删除Java中包含2个子节点的节点

1 个答案: