數據結構----鏈表實現字典結構

1. 概述

1. 通過內部封裝的鏈表，來實現字典結構。

2. 源碼

/**
 * 通過鏈表實現字典.
 */
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 this.key + " : " + this.value;
        }
    }

    private Node dummyHead;

    private int size;

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

    @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 pre = dummyHead;
        while (pre.next != null) {
            if (key.equals(pre.next.key)) {
                Node delNode = pre.next;
                pre.next = delNode.next;
                delNode.next = null;
                size--;

                return delNode.value;
            }

            pre = pre.next;
        }

        return null;
    }

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

        V oldValue = node.value;
        node.value = newValue;
        return oldValue;
    }

    @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;
    }

    @Override
    public String toString() {
        StringBuilder result = new StringBuilder();
        result.append(String.format("Map size: %d ", getSize()));
        Node cur = dummyHead.next;
        while (cur != null) {
            result.append(cur).append(" ===> ");
            cur = cur.next;
        }

        result.append("Null");
        return result.toString();
    }

    // 根據key獲取對應的節點
    private Node getNode(K key) {
        Node cur = dummyHead.next;
        while (cur != null) {
            if (key.equals(cur.key)) {
                return cur;
            }

            cur = cur.next;
        }

        return null;
    }
}