在Java中是否有标准的Java库类来表示树?
具体来说，我需要表示以下内容:
任意节点上的子树可以有任意数量的子树 每个节点(根节点之后)及其子节点都有字符串值 我需要得到一个给定节点的所有子(某种类型的列表或字符串数组)，它的字符串值(即。一个方法，将一个节点作为输入，并返回子节点的所有字符串值作为输出)
是否有任何可用的结构，或者我需要创建我自己的(如果是这样，实施建议将是伟大的)。
当前回答
请检查下面的代码，其中我使用了Tree数据结构，没有使用Collection类。代码可能有bug /改进，但请使用这只是作为参考
package com.datastructure.tree;
public class BinaryTreeWithoutRecursion <T> {
private TreeNode<T> root;
public BinaryTreeWithoutRecursion (){
root = null;
}
public void insert(T data){
root =insert(root, data);
}
public TreeNode<T> insert(TreeNode<T> node, T data ){
TreeNode<T> newNode = new TreeNode<>();
newNode.data = data;
newNode.right = newNode.left = null;
if(node==null){
node = newNode;
return node;
}
Queue<TreeNode<T>> queue = new Queue<TreeNode<T>>();
queue.enque(node);
while(!queue.isEmpty()){
TreeNode<T> temp= queue.deque();
if(temp.left!=null){
queue.enque(temp.left);
}else
{
temp.left = newNode;
queue =null;
return node;
}
if(temp.right!=null){
queue.enque(temp.right);
}else
{
temp.right = newNode;
queue =null;
return node;
}
}
queue=null;
return node;
}
public void inOrderPrint(TreeNode<T> root){
if(root!=null){
inOrderPrint(root.left);
System.out.println(root.data);
inOrderPrint(root.right);
}
}
public void postOrderPrint(TreeNode<T> root){
if(root!=null){
postOrderPrint(root.left);
postOrderPrint(root.right);
System.out.println(root.data);
}
}
public void preOrderPrint(){
preOrderPrint(root);
}
public void inOrderPrint(){
inOrderPrint(root);
}
public void postOrderPrint(){
inOrderPrint(root);
}
public void preOrderPrint(TreeNode<T> root){
if(root!=null){
System.out.println(root.data);
preOrderPrint(root.left);
preOrderPrint(root.right);
}
}
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
BinaryTreeWithoutRecursion <Integer> ls= new BinaryTreeWithoutRecursion <>();
ls.insert(1);
ls.insert(2);
ls.insert(3);
ls.insert(4);
ls.insert(5);
ls.insert(6);
ls.insert(7);
//ls.preOrderPrint();
ls.inOrderPrint();
//ls.postOrderPrint();
}
}
其他回答
Java中有一些树数据结构，比如JDK Swing中的DefaultMutableTreeNode, Stanford解析器包中的tree，以及其他一些玩具代码。但这些都不够，也不够小，不能用于一般用途。
Java tree项目试图在Java中提供另一种通用的树数据结构。这个和其他的区别是
Totally free. You can use it anywhere (except in your homework :P) Small but general enough. I put everything of the data structure in one class file, so it would be easy to copy/paste. Not just a toys. I am aware of dozens of Java tree codes that can only handle binary trees or limited operations. This TreeNode is much more than that. It provides different ways of visiting nodes, such as preorder, postorder, breadthfirst, leaves, path to root, etc. Moreover, iterators are provided too for the sufficiency. More utils will be added. I am willing to add more operations to make this project comprehensive, especially if you send a request through github.
请检查下面的代码，其中我使用了Tree数据结构，没有使用Collection类。代码可能有bug /改进，但请使用这只是作为参考
package com.datastructure.tree;
public class BinaryTreeWithoutRecursion <T> {
private TreeNode<T> root;
public BinaryTreeWithoutRecursion (){
root = null;
}
public void insert(T data){
root =insert(root, data);
}
public TreeNode<T> insert(TreeNode<T> node, T data ){
TreeNode<T> newNode = new TreeNode<>();
newNode.data = data;
newNode.right = newNode.left = null;
if(node==null){
node = newNode;
return node;
}
Queue<TreeNode<T>> queue = new Queue<TreeNode<T>>();
queue.enque(node);
while(!queue.isEmpty()){
TreeNode<T> temp= queue.deque();
if(temp.left!=null){
queue.enque(temp.left);
}else
{
temp.left = newNode;
queue =null;
return node;
}
if(temp.right!=null){
queue.enque(temp.right);
}else
{
temp.right = newNode;
queue =null;
return node;
}
}
queue=null;
return node;
}
public void inOrderPrint(TreeNode<T> root){
if(root!=null){
inOrderPrint(root.left);
System.out.println(root.data);
inOrderPrint(root.right);
}
}
public void postOrderPrint(TreeNode<T> root){
if(root!=null){
postOrderPrint(root.left);
postOrderPrint(root.right);
System.out.println(root.data);
}
}
public void preOrderPrint(){
preOrderPrint(root);
}
public void inOrderPrint(){
inOrderPrint(root);
}
public void postOrderPrint(){
inOrderPrint(root);
}
public void preOrderPrint(TreeNode<T> root){
if(root!=null){
System.out.println(root.data);
preOrderPrint(root.left);
preOrderPrint(root.right);
}
}
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
BinaryTreeWithoutRecursion <Integer> ls= new BinaryTreeWithoutRecursion <>();
ls.insert(1);
ls.insert(2);
ls.insert(3);
ls.insert(4);
ls.insert(5);
ls.insert(6);
ls.insert(7);
//ls.preOrderPrint();
ls.inOrderPrint();
//ls.postOrderPrint();
}
}
Java中没有适合您需求的特定数据结构。您的需求非常具体，因此需要设计自己的数据结构。看看你的需求，任何人都可以说你需要某种具有特定功能的n元树。你可以通过以下方式设计你的数据结构:
Structure of the node of the tree would be like content in the node and list of children like: class Node { String value; List children;} You need to retrieve the children of a given string, so you can have 2 methods 1: Node searchNode(String str), will return the node that has the same value as given input (use BFS for searching) 2: List getChildren(String str): this method will internally call the searchNode to get the node having same string and then it will create the list of all string values of children and return. You will also be required to insert a string in tree. You will have to write one method say void insert(String parent, String value): this will again search the node having value equal to parent and then you can create a Node with given value and add to the list of children to the found parent.
我建议，你写一个类的节点结构类节点{字符串值;在另一个NodeUtils类中列出children;}和所有其他方法，如search, insert和getChildren，这样你也可以传递树的根来对特定的树执行操作，例如: 类NodeUtils{公共静态节点搜索(节点根，字符串值){//执行BFS并返回节点}
在过去，我只是为此使用了一个嵌套映射。这是我今天用的，它很简单，但它符合我的需要。也许这能帮到另一个人。
import com.fasterxml.jackson.annotation.JsonValue;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;
/**
* Created by kic on 16.07.15.
*/
public class NestedMap<K, V> {
private final Map root = new HashMap<>();
public NestedMap<K, V> put(K key) {
Object nested = root.get(key);
if (nested == null || !(nested instanceof NestedMap)) root.put(key, nested = new NestedMap<>());
return (NestedMap<K, V>) nested;
}
public Map.Entry<K,V > put(K key, V value) {
root.put(key, value);
return (Map.Entry<K, V>) root.entrySet().stream().filter(e -> ((Map.Entry) e).getKey().equals(key)).findFirst().get();
}
public NestedMap<K, V> get(K key) {
return (NestedMap<K, V>) root.get(key);
}
public V getValue(K key) {
return (V) root.get(key);
}
@JsonValue
public Map getRoot() {
return root;
}
public static void main(String[] args) throws Exception {
NestedMap<String, Integer> test = new NestedMap<>();
test.put("a").put("b").put("c", 12);
Map.Entry<String, Integer> foo = test.put("a").put("b").put("d", 12);
test.put("b", 14);
ObjectMapper mapper = new ObjectMapper();
System.out.println(mapper.writeValueAsString(test));
foo.setValue(99);
System.out.println(mapper.writeValueAsString(test));
System.out.println(test.get("a").get("b").getValue("d"));
}
}
例如:
import java.util.ArrayList;
import java.util.List;
/**
*
* @author X2
*
* @param <T>
*/
public class HisTree<T>
{
private Node<T> root;
public HisTree(T rootData)
{
root = new Node<T>();
root.setData(rootData);
root.setChildren(new ArrayList<Node<T>>());
}
}
class Node<T>
{
private T data;
private Node<T> parent;
private List<Node<T>> children;
public T getData() {
return data;
}
public void setData(T data) {
this.data = data;
}
public Node<T> getParent() {
return parent;
}
public void setParent(Node<T> parent) {
this.parent = parent;
}
public List<Node<T>> getChildren() {
return children;
}
public void setChildren(List<Node<T>> children) {
this.children = children;
}
}
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