1.3.28

question:

develop a recusive solution to the previous question.

answer:

import edu.princeton.cs.algs4.*;

public class Linklist
{
    private static class Node//节点
    {
        int 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 number of node " + i + ":");
            p2.item = StdIn.readInt();
            if(head == null)
            {
               head = p1 = p2;
            }
            else
            {
               p1.next = p2;
               p1 = p2;
            }
        }
        if(head != null)
        {
           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 int max(Node current, int max_num)
    {
        
        if(current == null)
        {
            return max_num;
        }
        else
        {
            max_num = max_num > current.item ? max_num : current.item;
            return max(current.next, max_num); 
        }
    }
    
    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 current = head;
        if(current == null)
        {
            StdOut.println("the max num is " + 0);
        }
        else
        {
            int max_num = current.item;
            max_num = linklist.max(current, max_num);
            StdOut.println("the max num is " + max_num);
        }
    }
}