java中实现树

实现一颗树，采用数组的存储方式，将树中的节点用Node类表示，方便与操作。
首先，整棵树的数组结构如下表所示，根节点的无父节点，用“-1”表示。

index	Data	parent
0	A	-1
1	B	0
2	C	0
3	D	0
4	E	1
5	F	1
6	G	5

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其次，定义一个节点Node类，用来存储每个节点的内容

package my.tree;

public class Node<T> {
    private T data;
    private int parent;

    public Node(){
    }

    public Node(T data){
        this.data = data;
    }

    public Node(T data,int parent){
        this.data = data;
        this.parent = parent;
    }

    public void setData(T data){
        this.data = data;
    }

    public T getData(){
        return this.data;
    }

    public void setParent(int parent){
        this.parent = parent;
    }

    public int getParent(){
        return this.parent;
    }
}

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开始实现树，提供基本的插入节点、获取所有节点、获取树的深度操作（着重）这些将数组大小设置为2，主要是考虑数组能否自动扩容;

package my.tree;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class MyTree<T> {
    private final int DEFAULT_SIZE = 2;
    private int size;
    private int count;
    private Object[] nodes;

    public MyTree() {
        this.size = this.DEFAULT_SIZE;
        this.nodes = new Object[this.size];
        this.count = 0;
    }

    public MyTree(Node<T> root) {
        this();
        this.count = 1;
        this.nodes[0] = root;
    }

    public MyTree(Node<T> root, int size) {
        this.size = size;
        this.nodes = new Object[this.size];
        this.count = 1;
        this.nodes[0] = root;
    }

    //添加一个节点
    public void add(Node<T> node) {
        for (int i = 0; i < this.size; i++) {
            if (this.nodes[i] == null) {
                nodes[i] = node;
                break;
            }
        }
        this.count++;
    }

    public void check(){
        if(this.count >= this.size){
            this.enlarge();
        }
    }
    //添加一个节点，并指明父节点
    public void add(Node<T> node, Node<T> parent) {
        this.check();
        node.setParent(this.position(parent));
        this.add(node);
    }

    //获取节点在数组的存储位置
    public int position(Node<T> node) {
        for (int i = 0; i < this.size; i++) {
            if (nodes[i] == node) {
                return i;
            }
        }
        return -1;
    }

    //获取整棵树有多少节点
    public int getSize(){
        return this.count;
    }

    //获取根节点
    @SuppressWarnings("unchecked")
    public Node<T> getRoot(){
        return (Node<T>) this.nodes[0];
    }

    //获取所以节点，以List形式返回
    @SuppressWarnings("unchecked")
    public List<Node<T>> getAllNodes(){
        List<Node<T>> list = new ArrayList<Node<T>>();
        for(int i=0;i<this.size;i++){
            if(this.nodes[i] != null){
                list.add((Node<T>)nodes[i]);
            }
        }
        return list;
    }

    //获取树的深度，只有根节点时为1
    @SuppressWarnings("unchecked")
    public int getDepth(){

        int max = 1;
        if(this.nodes[0] == null){
            return 0;
        }

        for(int i=0;i<this.count;i++){
            int deep = 1;
            int location = ((Node<T>)(this.nodes[i])).getParent();
            while(location != -1 && this.nodes[location] != null){
                location = ((Node<T>)(this.nodes[location])).getParent();
                deep++;
            }
            if(max < deep){
                max = deep;
            }
        }
        return max;
    }

    public void enlarge(){
        this.size = this.size + this.DEFAULT_SIZE;
        Object[] newNodes = new Object[this.size];
        newNodes = Arrays.copyOf(nodes, this.size);
        Arrays.fill(nodes, null);
        this.nodes = newNodes;
        System.out.println("enlarge");
    }
}

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最后，使用MyTreeClient来测试下，基本功能是否都已经实现;

package my.tree;

public class MyTreeClient {
    public static void main(String[] args){
        Node<String> root = new Node<String>("A",-1);
        MyTree<String> tree = new MyTree<String>(root);
        Node<String> b = new Node<String>("B");
        Node<String> c = new Node<String>("C");
        Node<String> d = new Node<String>("D");
        Node<String> e = new Node<String>("E");
        Node<String> f = new Node<String>("F");
        Node<String> g = new Node<String>("G");
        tree.add(b,root);
        tree.add(c,root);
        tree.add(d,root);

        tree.add(e,b);
        tree.add(f,b);
        tree.add(g,f);


        System.out.println(tree.getSize());
        System.out.println(tree.getRoot().getData());
        System.out.println(tree.getAllNodes());
        System.out.println(tree.getDepth());
        tree.add(new Node<String>("H"),g);
        System.out.println(tree.getDepth());
        tree.enlarge();
    }
}