用Java构造二叉树

Question

我正在构建一个二叉树.如果这是一种正确的方法,请告诉我.如果没有请告诉我如何？我找不到构建一般二叉树的正确链接.BST到处都是编码的.

  3
 / \
1   4
   / \
  2   5

这是我想要制作的二叉树.我应该能够完成所有的树遍历.简单的东西.

public class Binarytreenode
{
    public Binarytreenode left;
    public Binarytreenode right;
    public int data;

    public Binarytreenode(int data)
    {
        this.data=data;
    }

    public void printNode()
    {
        System.out.println(data);
    }

    public static void main(String ar[])
    {
        Binarytreenode root = new Binarytreenode(3);
        Binarytreenode n1 = new Binarytreenode(1);
        Binarytreenode n2 = new Binarytreenode(4);
        Binarytreenode n3 = new Binarytreenode(2);
        Binarytreenode n4 = new Binarytreenode(5);

        root.left = n1;
        root.right = n2;
        root.right.left = n3;
        root.right.right = n4;
    }
}

Answer 1

我认为这就是你要找的东西:

public class Binarytree
{
    private static Node root;

    public Binarytree(int data)
    {
        root = new Node(data);
    }

    public void add(Node parent, Node child, String orientation)
    {
        if (orientation.equals("left"))
        {
           parent.setLeft(child);
        }
        else
        {
            parent.setRight(child);
        }
    }

    public static void main(String args[])
    {
        Node n1 = new Node(1);
        Node n2 = new Node(4);
        Node n3 = new Node(2);
        Node n4 = new Node(5);

        Binarytree tree = new Binarytree(3); //  3
        tree.add(root, n1, "left"); //         1/ \
        tree.add(root, n2, "right"); //            4
        tree.add(n2, n3, "left"); //             2/ \
        tree.add(n2, n4, "right"); //                5
    }
}

class Node {
    private int key;
    private Node left;
    private Node right;

    Node (int key) {
        this.key = key;
        right = null;
        left = null;
    }

    public void setKey(int key) {
        this.key = key;
    }

    public int getKey() {
        return key;
    }

    public void setLeft(Node left) {
        this.left = left;
    }

    public Node getLeft() {
        return left;
    }

    public void setRight(Node right ) {
        this.right = right;
    }

    public Node getRight() {
        return right;
    }

}

Answer 2

二叉树背后的想法是它被排序.任何大于当前值的值都在右侧节点中,每个小值都在左侧节点中.这意味着您不应该在主程序中进行树构建.相反,每个节点都应该有一个"插入"方法,用于确定新节点是应该转到当前节点的左侧还是右侧.如果有新节点,则创建该节点,然后调用root.insert(newNode).

然后insert方法就像这样工作(因为这显然是学生作业,你应该从中学习,你只能得到我的伪代码,没有完整的解决方案):

When value is smaller than own value:
     When there already is a left-node:
         call left-node.insert(new-node)
     When there isn't a left-node yet:
         the left-node is now the new-node
When value is larger than own value:
     When there already is a right-node:
         call right-node.insert(new-node)
     When there isn't a right-node yet:
         the right-node is now the new-node
When value is equal to own value:
     Duplicate value. Either ignore the value or throw an exception.

查找对象是否已在树中的工作方式相同:

When requested value is equal to the value of this node
     return this node
When the requested value is smaller
     When a left node exists
         call left.find(value)         
     When no left node exists
          value doesn't exist in this tree
When the requested value is larger
     When a right node exists
         call right.find(value)         
     When no right node exists
          value doesn't exist in this tree

如果您实际上并不想了解二叉树如何工作而只是使用它们,那么只需使用TreeSet,这是一个已经在工作的二叉树实现.