基于链表或二分搜索树实现Map映射(java语言版)

基于链表实现Map

/**
 * @author BestQiang
 */
public class LinkedListMap<K, V> implements Map<K, V> {

    private class Node {
        public K key;
        public V value;
        public Node next;

        public Node(K key, V value, Node next) {
            this.key = key;
            this.value = value;
            this.next = next;
        }

        public Node(K key) {
            this(key, null, null);
        }

        public Node() {
            this(null, null, null);
        }

        @Override
        public String toString() {
            return key.toString() + " : " + value.toString();
        }
    }

    private Node dummyHead;
    private int size;

    public LinkedListMap() {
        dummyHead = new Node();
        size = 0;
    }

    @Override
    public void add(K key, V value) {
        Node node = getNode(key);
        if (node == null) {
            dummyHead.next = new Node(key, value, dummyHead.next);
            size ++;
        } else {
            node.value = value;
        }

    }

    @Override
    public V remove(K key) {
        Node prev = dummyHead;
        while (prev.next != null) {
            if (prev.next.key.equals(key)) {
                break;
            }
            prev = prev.next;
        }
        if (prev.next != null) {
            Node delNode = prev.next;
            prev.next = delNode.next;
            delNode.next = null;
            size --;
            return delNode.value;
        }
        return null;
    }

    public Node getNode(K key) {
        Node cur = dummyHead.next;
        while (cur != null) {
            if (cur.key.equals(key)) {
                return cur;
            }
            cur = cur.next;
        }
        return null;
    }

    @Override
    public boolean contains(K key) {
        if (getNode(key) != null)
            return true;
        return false;
    }

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

    @Override
    public void set(K key, V newValue) {
        Node node = getNode(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;
    }
}

基于二分搜索树实现Map

/**
 * @author BestQiang
 */
public class BSTMap<K extends Comparable, V> implements Map<K, V> {

    private 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;
    }

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

    // 返回一node为根节点的二分搜索树中,key所在的节点
    private Node getNode(Node node, K key) {
        if (node == null) {
            return null;
        }
        if (key.equals(node.key)) {
            return node;
        } else if (key.compareTo(node.key) < 0) {
            return getNode(node.left, key);
        } else //if (key.compareTo(node.key) > 0)
            return getNode(node.right, key);

    }

    @Override
    public V remove(K key) {
        return null;
    }

    @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;
    }

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

    // 返回以node为根的二分搜索树的最小值所在的节点
    private Node getMin(Node node) {
        if (node.left == null) {
            return node;
        }
        return getMin(node.left);
    }

    // 删除掉以node为根的二分搜索树中的最小节点
    // 返回删除节点后新的二分搜索树的根
    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 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 {   // key.compareTo(node.key) == 0

            // 待删除节点左子树为空的情况
            if (node.left == null) {
                Node rightNode = node.right;
                node.right = null;
                size--;
                return rightNode;
            }

            // 待删除节点右子树为空的情况
            if (node.right == null) {
                Node leftNode = node.left;
                node.left = null;
                size--;
                return leftNode;
            }

            // 待删除节点左右子树均不为空的情况

            // 找到比待删除节点大的最小节点, 即待删除节点右子树的最小节点
            // 用这个节点顶替待删除节点的位置
            Node successor = getMin(node.right);
            successor.right = removeMin(node.right);
            successor.left = node.left;

            node.left = node.right = null;

            return successor;
        }
    }


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

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

}