《Java数据结构与算法》笔记-CH5-链表-3双端链表

/**
 * 双端链表的实现
 */
class LinkA {
    public long dData;
    public LinkA next;

    public LinkA(long d) {
        dData = d;
    }

    public String toString() {
        return "[" + dData + "]";
    }

    public void displayLink() {
        System.out.println(toString());
    }
}

class FirstLastList {
    private LinkA first;// 头部
    private LinkA last;// 尾部

    public FirstLastList() {
        first = null;
        last = null;
    }

    public boolean isEmpty() {
        return first == null;
    }

    /**
     * 在头部插入节点
     */
    public void insertFirst(LinkA l) {
        if (isEmpty())
            last = l;
        l.next = first;
        first = l;
    }

    /**
     * 在尾部插入节点
     * 
     * @param l
     */
    public void insertLast(LinkA l) {
        if (isEmpty())
            first = l;
        else
            last.next = l;
        last = l;
    }

    /**
     * 从头部删除一个节点
     * 
     * @return
     */
    public long deleteFirst() {
        long temp = first.dData;
        if (first.next == null)
            last = null;
        first = first.next;
        return temp;
    }

    public String toString() {
        if (isEmpty())
            return "{}";
        LinkA current = first;
        StringBuilder sb = new StringBuilder();
        sb.append("{");
        while (current != null) {
            sb.append(current.toString()).append(",");
            if (current.next == null)
                break;
            else
                current = current.next;
        }
        sb.deleteCharAt(sb.length() - 1);
        sb.append("}");
        return sb.toString();
    }

    public void displayList() {
        System.out.println(toString());
    }
}

public class FirstLastListDemo {
    public static void main(String[] args) {
        FirstLastList fll = new FirstLastList();
        for (int i = 1; i < 10; i++) {
            System.out.println("插入:"+i);
            if (i % 2 == 0)//i为偶数调用insertFirst
                fll.insertFirst(new LinkA(i));
            else//i为基数调用insertLast
                fll.insertLast(new LinkA(i));
            fll.displayList();
        }
        System.out.println("插入完毕开始从头部删除");
        while(!fll.isEmpty()){
            fll.deleteFirst();
            fll.displayList();
        }
    }
}