java实现双向链表

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java实现双向链表

public class MLinkedList<T> {
    //元素个数
    private int size = 0;
    //头指针
    private Node<T> first;
    //尾指针
    private Node<T> last;

    @Data
    @AllArgsConstructor
    static class Node<T> {
        private T data;
        private Node<T> next;
        private Node<T> prev;
    }

    /**
     * 在链表头部加入元素
     *
     * @param t
     */
    public void addFirst(T t) {
        Node<T> node = this.first;
        Node<T> newNode = new Node<>(t, node, null);
        first = newNode;
        //判断加入节点之前的链表是否为空
        if (node == null) {
            last = newNode;
        } else {
            node.prev = newNode;
        }
        size++;
    }

    /**
     * 将数据加入到尾部
     *
     * @param t
     */
    public void addLast(T t) {
        Node<T> node = last;
        Node<T> newNode = new Node<>(t, null, node);
        last = newNode;
        if (node == null) {
            first = newNode;
        } else {
            node.next = newNode;
        }
        size++;
    }

    /**
     * 添加元素默认加到队尾
     *
     * @param t
     */
    public void add(T t) {
        addLast(t);
    }

    /**
     * 0 1 2
     * 在指定位置更新元素为新值,索引需要在0~size-1之间
     *
     * @param index
     * @param t
     */
    public void set(int index, T t) {
        rangeCheck(index);
        int cursor = 0;
        Node<T> tNode = this.first;
        while (cursor != index) {
            tNode = tNode.next;
            cursor++;
        }
        //循环结束，现在cursor=index,tNode就是要更新的节点
        tNode.data = t;
    }

    /**
     * insert不同于set,insert在指定位置插入节点，原来的节点后移
     * @param index
     * @param t
     */
    public void insert(int index,T t) {
        rangeCheck(index);
        if (index == 0) {
            addFirst(t);
            return;
        }
        int curIndex=0;
        Node<T> curNode = this.first;
        while (curIndex != index) {
            curNode=curNode.next;
            curIndex++;
        }
        Node<T> prev = curNode.prev;
        Node<T> newNode = new Node<>(t, curNode, prev);
        prev.next=newNode;
        curNode.prev=newNode;
        size++;
    }

    /**
     * 删除指定数据
     *
     * @param t
     * @return
     */
    public T remove(T t) {
        Node<T> tNode = this.first;
        while (tNode != null && !tNode.data.equals(t)) {
            tNode = tNode.next;
        }
        //走到这里可能是找到了，也可能到头了

        if (tNode == null) {
            return null;
        }
        //如果tNode！=null,说明找到指定节点了
        Node<T> prev = tNode.prev;
        Node<T> next = tNode.next;
        prev.next = next;
        next.prev = prev;
        size--;
        return t;

    }

    /**
     * 删除指定位置的数据
     * @param i 索引
     * @return
     */
    public T removeAt(int i) {
        rangeCheck(i);
        int curIndex=0;
        Node<T> tNode = this.first;
        while (tNode != null && curIndex!=i) {
            tNode = tNode.next;
            curIndex++;
        }
        //走到这里可能是找到了，也可能到头了

        if (tNode == null) {
            return null;
        }
        //如果tNode！=null,说明找到指定节点了
        Node<T> prev = tNode.prev;
        Node<T> next = tNode.next;
        prev.next = next;
        next.prev = prev;
        size--;
        return tNode.data;

    }

    /**
     * 校验新增和删除元素的索引范围
     *
     * @param index
     */
    private void rangeCheck(int index) {
        if (index < 0 || index > size - 1) {
            throw new IndexOutOfBoundsException("下标越界");
        }
    }

    /**
     * 搜索数据
     *
     * @param x
     * @return
     */
    public Node<T> search(T x) {
        Node<T> cursor = first;
        while (cursor != null && cursor.data != x) {
            cursor = cursor.next;
        }
        return cursor;
    }

    /**
     * 将链表转成数组
     *
     * @return
     */
    public Object[] toArray() {
        Object[] objects = new Object[size];
        int count = 0;
        objects[count] = first.data;
        Node<T> cursor = first;
        while (cursor.next != null) {
            count++;
            cursor = cursor.next;
            objects[count] = cursor.data;
        }
        return objects;
    }


    @Override
    public String toString() {
        return Arrays.toString(toArray());
    }

    public static void main(String[] args) {
        MLinkedList<Integer> MLinkedList = new MLinkedList<>();
        MLinkedList.addLast(1);
        MLinkedList.addLast(2);
        MLinkedList.addLast(3);
        MLinkedList.addFirst(0);
        MLinkedList.addFirst(-1);
        MLinkedList.addFirst(-2);
        System.out.println(MLinkedList);
        MLinkedList.set(2, 100);
        System.out.println(MLinkedList);
        MLinkedList.remove(100);
        System.out.println(MLinkedList);
        MLinkedList.insert(4,400);
        System.out.println(MLinkedList);
        MLinkedList.insert(0,99);
        System.out.println(MLinkedList);
        MLinkedList.removeAt(3);
        System.out.println(MLinkedList);

    }
}

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