双向链表简单实现--数据结构与算法纪录片第一记

　　从这个月开始得准备春招的东西，所以打算重新学习数据结构与算法，以后的博客就以这个为主。

　　今天是线性结构中的双向链表。

　　代码实现与测试：

　　DoubleLinkNode：　

package linear.doublelink;

/**
 * @Description: 链表节点结构体
 * @Auther: Weijie.Zhang
 * @Date: 2018/11/1 17:03
 */
public class DoubleLinkNode<T> {
    public T value;
    public DoubleLinkNode pre;
    public DoubleLinkNode next;

    public DoubleLinkNode(T value) {
        this.value = value;
    }

    public DoubleLinkNode(T value, DoubleLinkNode pre, DoubleLinkNode next) {
        this.value = value;
        this.pre = pre;
        this.next = next;
    }
}

DoubleLink：

package linear.doublelink;

/**
 * @Description: 链表实现
 * @Auther: Weijie.Zhang
 * @Date: 2018/11/1 17:04
 */
public class DoubleLink<T> {
    //表头
    private DoubleLinkNode<T> head;
    //节点个数
    private int count;

    public DoubleLink() {
        head = new DoubleLinkNode<T>(null, null, null);
        head.pre = head.next = head;
        count = 0;
    }

    //返回节点个数
    public int size() {
        return count;
    }

    //返回链表是否为空
    public Boolean isEmpty() {
        if (count == 0) {
            return true;
        } else {
            return false;
        }
    }

    //获取第index位置上的节点
    public DoubleLinkNode<T> get(int index) {
        if (index < 0 || index >= count) {
            System.out.println("索引超出范围");
            throw new IndexOutOfBoundsException();
        }

        //正向查找
        if (index <= count / 2) {
            DoubleLinkNode doubleLinkNode = head.next;
            for (int i = 0; i < index; i++)
                doubleLinkNode = doubleLinkNode.next;
            return doubleLinkNode;
        }

        //反向查找
        DoubleLinkNode doubleLinkNode = head.pre;
        int pos = count - index - 1;
        for (int i = 0; i < pos; i++)
            doubleLinkNode = doubleLinkNode.pre;
        return doubleLinkNode;
    }

    //获取第一个节点的值
    public T getFirstValue() {
        return get(0).value;
    }

    //获取最后一个节点的值
    public T getLastValue() {
        return get(count - 1).value;
    }

    //获取第index节点的值
    public T getIndexValue(int index) {
        return get(index).value;
    }

    //将节点插入到index位置
    public void insert(int index, DoubleLinkNode<T> doubleLinkNode) {
        if (index < 0 || index > count) {
            System.out.println("超出索引范围");
            throw new IndexOutOfBoundsException();
        }

        if (index == 0) {
            head.next.pre = doubleLinkNode;
            head.next = doubleLinkNode;
            count++;
            return;
        }

        if (index == count) {
            doubleLinkNode.next = head;
            doubleLinkNode.pre = head.pre;
            head.pre.next = doubleLinkNode;
            head.pre = doubleLinkNode;
            count++;
            return;
        }

        for (int i = 0; i < index; i++) {
            DoubleLinkNode linkNode = get(index);
            doubleLinkNode.pre = linkNode.pre;
            doubleLinkNode.next = linkNode;
            linkNode.pre.next = doubleLinkNode;
            linkNode.pre = doubleLinkNode;
            count++;
            return;
        }
    }

    //删除index上的节点
    public void delete(int index) {
        DoubleLinkNode doubleLinkNode = get(index);
        doubleLinkNode.pre.next = doubleLinkNode.next;
        doubleLinkNode.next.pre = doubleLinkNode.pre;
        count--;
        return;
    }

    //修改index节点上的值
    public void change(int index, T value) {
        get(index).value = value;
        return;
    }
}

MainTest：

package linear.doublelink;

/**
 * @Description: 测试
 * @Auther: Weijie.Zhang
 * @Date: 2018/11/1 17:57
 */
public class MainTest {
    public static void main(String[] args) {
        DoubleLink<Integer> doubleLink = new DoubleLink<>();
        int i;
        for (i = 0; i < 10; i++) {
            DoubleLinkNode<Integer> doubleLinkNode = new DoubleLinkNode<>(i + 22);
            doubleLink.insert(i, doubleLinkNode);
        }
        System.out.println(doubleLink.getFirstValue());
        System.out.println(doubleLink.getLastValue());
        System.out.println(doubleLink.getIndexValue(7));

        doubleLink.delete(4);
        doubleLink.insert(9,new DoubleLinkNode<Integer>(10));

        for (int j = 0; j < doubleLink.size(); j++) {
            System.out.print(doubleLink.get(j).value + "    ");
        }
    }
}