1.3.25

import edu.princeton.cs.algs4.*;

public class Linklist
{
    private static class Node//节点
    {
        String item;
        Node next = null;
    }
    
     public Node create(int n)//创建链表
    {
        Node head = null;
        Node p1 = head;
        Node p2;
        for(int i = 0; i < n; i++)
        {
            p2 = new Node();
            StdOut.println("input the string of node " + i + ":");
            p2.item = StdIn.readString();
            if(head == null)
            {
               head = p1 = p2;
            }
            else
            {
               p1.next = p2;
               p1 = p2;
            }
        }
        p1.next = null;
        return head;
    }
   
    public void show(Node head)//遍历链表
    {
        Node current = head;
        while(current != null)
        {
            StdOut.print(current.item + "\t");
            current= current.next;
        }
        StdOut.print("\n");
    }
    
    public void insertafter(Node head, Node first, Node second)
    {
        if(first == null || second == null)
        {
            return;
        }
        Node current = head;
        while(current != null)//原链表里找first节点
        {
            if(current.equals(first))//找到后插入second节点
            {
                Node temp = current.next;
                current.next = second;
                second.next = temp;
            }
            current = current.next;
        }
        return;
    }
    
    public static void main(String[] args)
    {
        Node head;
        int n;
        Linklist linklist = new Linklist();
        StdOut.println("input the length of linklist:(>0)");
        n = StdIn.readInt();
        head = linklist.create(n);
        linklist.show(head);
        Node second = new Node();
        StdOut.println("input the string item of second node");
        second.item = StdIn.readString();
        second.next = null;
        StdOut.println("input the c to insert after cth node:");//即first,且从第0个开始
        int c = StdIn.readInt();
        Node first = head;
        while(c>0)
        {
            first = first.next;
            c--;
        }
        linklist.insertafter(head,first,second);
        linklist.show(head);
    }
}