JAVA數據結構之LinkedListMap

LinkedListMap

• 底層用LinkedList實現Map

public class LinkedListMap<K,V> implements Map<K,V>{
//內部定義節點
    private class Node<K,V>{
        public K key;
        public V value;
        public Node next;

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

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

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

        @Override
        public String toString(){
        return "Node{" +
                    "key=" + key +
                    ", value=" + value +
                    ", next=" + next +
                    '}';
        }

    }   

    private Node dummyHead;
    private int size;

    /***構造函數**/
    public LinkedListMap(){
        size = 0;
        dummyHead = new Node<>();
    }

     @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;
    }

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

    @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 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 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 = prev.next.next;
            //斷鏈 ，不能直接賦值null ，因爲要返回key
            delNode.next = null;
            size--;
            return (V)delNode.value;
        }
        return null;
    }
}