【数据结构】Map 映射

数据结构源码

接口

public interface Map<K, V> {

    void add(K key, V value);

    V remove(K key);

    boolean contains(K key);

    V get(K key);

    void set(K key, V value);

    int getSize();

    boolean isEmpty();

}

实现类

public class LinkedListMap<K, V> implements Map<K, V> {

    /**
     * 内部类，定义结点Node
     */
    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, V value){
            this(key, value, 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;
    }

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

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

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

        node.value = value;
    }

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

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

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

数据结构拆解

维护字段和内部类

    /**
     * 内部类，定义结点Node
     */
    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, V value){
            this(key, value, null);
        }

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

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

    private Node dummyHead;

    private int size;
    

构造函数

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

增

    @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;
        }
    }

删

    @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;
    }

改

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

        node.value = value;
    }

查

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

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

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

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

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