Java:二分検索ツリーに基づくMap

ガイド:本文は3つの部分に分かれています.

カスタムMapインタフェース

Mapの二分探索ツリーは

を実現する.

コード機能テスト

一.カスタムMapインタフェース

public interface Map {

    void add(K key, V value);
    
    V remove(K key);
    
    boolean contains(K key);
    
    V get(K key);
    
    void set(K key, V newValue);
    
    int getSize();
    
    boolean isEmpty();
}

二.Mapの二分探索ツリー実装

ublic class BSTMap, V> implements Map {

    public class Node {
        public K key;
        public V value;
        public Node left, right;

        public Node (K key, V value){
            this.key = key;
            this.value = value;
            left = null;
            right = null;
        }
    }

    private Node root;
    private int size;

    public BSTMap(){
        root = null;
        size = 0;
    }

    //             (key, value)
    @Override
    public void add(K key, V value) {
        root = add(root, key, value);
    }

    //   node             (key, value),     
    //                
    private Node add(Node node, K key, V value){

        if (node == null){
            size++;
            return new Node(key, value);
        }

        if (key.compareTo(node.key) < 0){
            node.left = add(node.left, key, value);
        }else if (key.compareTo(node.key) > 0){
            node.right = add(node.right, key, value);
        }else
            node.value = value;
        return node;
    }

    //    node           , key     
    private Node getNode(Node node, K key){
        if (node == null)
            return null;

        if (key.compareTo(node.key) == 0){
            return node;
        }
        else if (key.compareTo(node.key) > 0){
            return getNode(node.right, key);
        }
        else
            return getNode(node.left, key);
    }


    @Override
    public boolean contains(K key) {
        return getNode( root, key) == null;
    }

    @Override
    public V get(K key) {
        Node node = getNode(root, key);
        return node == null?null : node.value;
    }

    //           key   
    @Override
    public void set(K key, V newValue) {
        Node node = getNode(root, key);
        if (node == null)
            throw new IllegalArgumentException(key + " doesn't exist!");

        node.value = newValue ;
    }

    @Override
    public int getSize() {
        return size;
    }

    @Override
    public boolean isEmpty() {
        return size==0;
    }

    //            key   
    @Override
    public V remove(K key) {
        Node node = getNode(root, key);
        if (node != null){
            root = remove(root, key);
            return node.value;
        }
        return null;
    }

    //     node           key   ,     
    //          root
    private Node remove(Node node, K key){
        if (node == null)
            return null;

        if (key.compareTo(node.key) < 0) {
            node.left = remove(node.left, key);
            return node;
        }
        else if (key.compareTo(node.key) > 0) {
            node.right = remove(node.right, key);
            return node;
        }
        else{
            //         
            if (node.left == null){
                Node rightNode = node.right;
                node.right = null;
                size -- ;
                return rightNode;
            }

            //         
            if (node.right == null){
                Node leftNode = node.left;
                node.left = null;
                size -- ;
                return leftNode;
            }

            //            
            Node successor = minimum(node.right);
            successor.right = removeMin(node.right);
            successor.left = node.left;
            node.left = node.right = null;
        }
        return node;
    }

    //         
    private Node removeMin(Node node){

        if (node.left == null){
            Node rightNode = node.right;
            node.right = null;
            size -- ;
            return rightNode;
        }

        node.left = removeMin(node.left);
        return node;
    }

    //         
    private Node minimum(Node node){
        if (node.left == null)
            return node;
        return minimum(node.left);
    }
	
	//     
    public void  postOrder(){
        postOrder(root);
    }
	private void postOrder(Node node){
        if (node != null){
            postOrder(node.left);
            postOrder(node.right);
            System.out.print(node.key + ": " + node.value);
        }
    }
}

三.機能テストコード

public static void main(String[] args) {
        BSTMap map = new BSTMap<>();
        Random random = new Random();
        for (int i = 0; i < 20; i++) {
            map.add(random.nextInt(10), random.nextInt(10));
        }
        map.postOrder();
        System.out.println();
        map.set(1,map.get(8).intValue());
        System.out.println(map.remove(2));
        map.postOrder();
        System.out.println();
        System.out.println("size " + map.getSize());
    }