Java二叉搜索树插入方法不起作用

Question

我的 BST 插入方法有问题。它只是将我的姓名列表插入到左侧，而不是向右递归并适当平衡。这就是我的输出的样子。此姓名列表有 125 个姓名，因此我将其剪短以适合此窗口。在输出下面，我放入了 BST java 程序的 insert 方法的 java 代码，以及 main 方法的一部分。我希望有人能看到我的问题，因为我和我的导师找不到问题。

预购遍历:沃尔特:空 |-劳伦斯:空 |-Ken:空 |-詹妮弗:null |-大卫:空 |-沃尔特:null |-菲尔:空 |-斯科蒂:空 |-托德:空 |-伦纳德:空 |-卡拉:空 |-米歇尔:空 |-吉尔:空 |-史蒂文:空 |-永利:null |-劳埃德:空

public void insertLeft(E key, T value) {
    Node<E, T> node = new Node<E, T>(key, value);
    if (root == null) {
        root = node;
    } else {
        Node current = root;
        while (current.left != null) {
            current = current.left;
        }
        current.left = node;
    }
}

//User friendly THE ONLY THING THAT DOES NOT WORK!!!!!!!
public boolean insert(E key, T value) {
    return insert(root, key, value);
}

public boolean insert(Node position, E key, T value) {
    if (position == null) {
        root = new Node<E, T>(key, value);
        return true;
    }
    int comparison = position.key.compareTo(key);
    if (comparison > 0) {
        if (position.left == null) {;
            position.left = new Node<E, T>(key, value);
            return true;
        }
        return insert(position.left, key, value);
    } else if (comparison < 0) {
        if (position.right == null) {
            position.right = new Node<E, T>(key, value);
            return true;
        }
        return insert(position.right, key, value);
    } else {
        return false;
    }
}

public static void main(String[] args) { Main main = new Main();

    BinaryTree bst = new BinaryTree();
    //ADD DATA Oshiro stuff
    String namesList = "Walt Lawrence Ken Jennifer David Walter Phil Scotty "
            + "Todd Leonard Kara Michelle Jill Steven Wynn Lloyd Brandon Gary"
            + " Jim Dale Joyce Don Tom Christine Rachel Jeff Raymond Kelli"
            + " Charles Kevin Brant Joseph Michael Kelly Jessie Suzie Sally"
            + " Christian Terry John Art Francis Riki Evelyn Tony Ikaika Joe"
            + " Ann Neil Daniel Willie James Jeremy Aislynn Larry Celeste"
            + " Paige Dennis Fred Rosa Ryan George Gabe Lance Carolyn Mariah"
            + " Hal Christina Christopher Mark Stephen Stanley Sharon Hannah"
            + " Gregory Barry Kawika Greg Derek Philip Alfredo Jillian Joedie"
            + " Anthony Kyle Bradley Masa Clyde Robert Zachary Jaron Fernando"
            + " Kosuke Becky Dora Rheada Ashley Dustin Joshuah Ricardo Pete"
            + " Katrina Arwin Mica Arlene Venus Jenny Nicole Jeylyn Trisha"
            + " Theresa Eric Terry Trenton Marcus Tristan Rueben Melvin"
            + " Kurtis Mary";
    //Use name for names and nameLength for number of names
    String[] nameData = namesList.split("\\s");
    boolean[] nameInsert = new boolean[nameData.length];
    for (String dataAdd : nameData) {
        bst.insertLeft(dataAdd, null);

    }
    System.out.println("\nThe Oshiro NamesList has been added to the tree, printing tree:");
    bst.traverse(1);
    System.out.println(bst.toString());

    Scanner userInput = new Scanner(System.in);
    System.out.println("Options available:"
            + "\n[0]Add the names to the tree"
            + "\n[1]Delete a name from the tree"
            + "\n[2]Print out contents of tree in alphabetical order"
            + "\n[3]Print out contents of tree in reverse alphabetical order"
            + "\n[4]Search the tree for a specific name and return number of probes"
            + "\n[5]Destroy the tree"
            + "\n[6]Balance the tree"
            + "\n[7]Draw the tree as loaded"
            + "\n[8]Draw the tree completely balanced"
            + "\n[9]Draw the tree"
            + "\n[10]Exit");
    int selection;

Answer 1

树向左生长，因为这就是您在代码中告诉它的内容

for(String dataAdd : nameData)
    bst.insertLeft(dataAdd, null);

insertLeft，顾名思义，只在左侧插入，将树更像是一个链表

public void insertLeft(E key, T value)
{
    Node<E, T> node = new Node<E, T>(key, value);
    if(root == null)
        root = node;
    else
    {
        Node current = root;
        while(current.left != null)
            current = current.left;
        current.left = node;
    }
}

insertLeft 方法的结构运行良好，在遍历树以添加到树之前，检查基本情况树是否为空 (root == null)左

如果您希望它作为排序树的插入(Binary S每个T树)，您可能希望对其进行一些编辑以考虑排序顺序

public void insertSorted(E key, T value)
{
    Node<E, T> node = new Node<E, T>(key, value);
    if(root == null) //keep the same base case
        root = node;
    else
    {
        Node current = root;
        while(true)
            if(node < current) //check left
                if(current.left == null) //set left
                {
                    current.left = node;
                    break;
                }
                else //iterate over left
                    current = current.left;
            else //check right
                if(current.right == null) //set right
                {
                    current.right = node;
                    break;
                }
                else //iterate over right
                    current = current.right;
    }
}

请注意，要在调用 insertSorted 后对树进行排序，树必须已经排序

另请注意，空树是排序的，就像只有 1 个节点的树一样