算法第四版 练习1.3.31

DoubleLinkList.java

import edu.princeton.cs.algs4.StdOut;

public class DoubleLinkList<Item> {
    private class DoubleNode<Item>
    {
        private DoubleNode<Item> next = null;
        private DoubleNode<Item> last = null;
        private Item data;
    }
    private DoubleNode<Item> head = null;
    public void push_back(Item item)
    {
        if (head == null)
        {
            head = new DoubleNode<Item>();
            head.data = item;
            return;
        }
        DoubleNode<Item> current = head;
        while (current.next != null)
            current = current.next;
        current.next = new DoubleNode<Item>();
        current.next.last = current;
        current.next.data = item;
    }
    public void push_fore(Item item)
    {
        if (head == null)
        {
            head = new DoubleNode<Item>();
            head.data = item;
            return;
        }
        DoubleNode<Item> n_head = new DoubleNode<Item>();
        n_head.data = item;
        n_head.next = head;
        head.last = n_head;
        head = n_head;
    }
    public void display()
    {
        if (head == null)
            return;
        DoubleNode<Item> current = head;
        while(current != null)
        {
            StdOut.print(current.data + " ");
            current = current.next;
        }
        StdOut.println();
    }
    public void remove_fore()
    {
        if (head == null)
            return;
        if (head.next == null)
        {
            head = head.next;
            return;
        }
        head = head.next;
        head.last = null;
    }
    public void remove_back()
    {
        DoubleNode<Item> current = head;
        while (current.next != null)
            current = current.next;
        current.last.next = null;
        current.last = null;
    }
    public void insert_before(DoubleNode<Item> nnode,DoubleNode<Item> pos)
    {
        if (pos == null || nnode == null)
            return;
        if (pos == head)
        {
            nnode.next = pos;
            pos.last = nnode;
            head = nnode;
            return;
        }
        nnode.next = pos;
        pos.last.next = nnode;
        nnode.last = pos.last.next;
        pos.last = nnode;
    }
    public void insert_after(DoubleNode<Item> nnode,DoubleNode<Item> pos)
    {
        if (nnode == null || pos == null)
            return;
        nnode.next = pos.next;
        nnode.last = pos;
        pos.next = nnode;
    }
    public void remove_before(DoubleNode<Item> pos)
    {
        if (pos == null)
            return;
        if (pos == head)
            return;
        if (pos == head.next)
        {
            head = head.next;
            return;
        }
        pos.last.last.next = pos;
        pos.last = pos.last.last;
    }
    public void remove_after(DoubleNode<Item> pos)
    {
        if (pos == null || pos.next == null)
            return;
        if (pos.next.next == null)
        {
            pos.next = null;
            return;
        }
        pos.next.next.last = pos;
        pos.next = pos.next.next;
    }
    //辅助接口函数
    public DoubleNode<Item> getPos(int i)
    {
        if (head == null)
            return null;
        if (i == 1)
            return head;
        int count = 1;
        DoubleNode<Item> current = head;
        while (current.next != null)
        {
            current = current.next;
            if (++count == i)
                return current;
        }
        return null;
    }
    public DoubleNode<Item> getNode(Item data)
    {
        DoubleNode<Item> ret = new DoubleNode<Item>();
        ret.data = data;
        return ret;
    }
}

测试:main.java

import edu.princeton.cs.algs4.StdOut;

public class Main {

    public static void main(String[] args)
    {
        DoubleLinkList<Integer> dl= new DoubleLinkList<Integer>();
        for (int i = 1; i <= 10; ++i)
            dl.push_back(i);
        dl.push_fore(0);
        dl.display();
        dl.remove_back();
        dl.remove_fore();
        dl.display();
        dl.remove_before(dl.getPos(2));
        dl.remove_after(dl.getPos(3));
        dl.display();
        dl.insert_before(dl.getNode(1), dl.getPos(1));
        dl.insert_after(dl.getNode(5),dl.getPos(4));
        dl.display();
    }
}