数据结构之双向列表实现

双向列表，这里无论删除还是增加都需要特别注意头节点与尾节点。

package shujujiegou;

/**
 * Created by lcc on 2017/6/30.
 */
public class BidirectionalList {
    public static void main(String[] args) {
        BidirectionalList list = new BidirectionalList();
        list.add("shaungqi");
        list.add("dadada");
        list.add("dadada1111");
        list.add(2, "xxx123");
        list.removeLast();
        System.out.println(list.getSize() + " " + list.get(2).data);
        list.add(1, "xxx123");
        System.out.println(list.getSize() + " " + list.get(2).data);
        list.remove(1);
        System.out.println(list.getSize() + " " + list.get(0).data);

    }


    Node first;
    Node last;
    private int size;

    public Node get(int i) {
        cheackBorder(i);
        Node getNode = first;
        for (int j = 0; j < i; j++) {
            getNode = getNode.next;
        }
        return getNode;
    }

    public void add(Object object) {
        Node addNode = new Node();
        addNode.data = object;
        if (first == null) {
            addNode.pre = null;
            addNode.next = null;
            first = addNode;
            last = addNode;
        } else {
            last.next = addNode;
            addNode.pre = last;
            addNode.next = null;
            last = addNode;
        }
        size++;
    }

    public void add(int i, Object object) {
        cheackBorder(i);

        Node addNode = new Node();
        addNode.data = object;

        Node getNode = get(i);

        if (i == size - 1) {
            last.next = addNode;
            addNode.pre = last;
            addNode.next = null;
            last = addNode;
        } else {
            Node next = getNode.next;
            getNode.next = addNode;
            addNode.pre = getNode;
            next.pre = addNode;
            addNode.next = next;
        }
        size++;
    }

    public Node removeLast() {
        Node oldLast = last;
        Node newLast = last.pre;
        last.pre = null;
        newLast.next = null;
        last = newLast;
        size--;
        return oldLast;
    }

    public Node remove(int i) {
        cheackBorder(i);
        Node removeNode = get(i);
        if (i == 0 && size == 1) {
            first = null;
        }
        else if (i == 0 && size != 1) {
            Node next =first.next;
            next.pre = null;
            first =next;
        } else{

            Node pre = removeNode.pre;
            Node next = removeNode.next;
            pre.next = next;
            next.pre = pre;
        }
        size--;
        return removeNode;
    }

    public void cheackBorder(int i) {
        if (i > size - 1) {
            try {
                throw new Exception("越界");
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    public int getSize() {
        return size;
    }
    public boolean  isExmpt() {
        return size ==0;
    }


    public class Node {
        Node pre;
        Object data;
        Node next;

        public Node() {

        }

        public Node(Node pre, Object data, Node next) {
            this.pre = pre;
            this.data = data;
            this.next = next;
        }

    }
}