在 Java 中制作链表

Question

I am adding elements in a Linked List via scanning the elements one by one using a for loop, but at the end there is a 0 coming while printing the list. The last node is pointing to null but still the list is having one element that is 0. I am providing my source code below and then inputs

import java.util.Scanner;
import static java.lang.System.out;
class Node{
    int data;
    Node next;
    Node(){
       this.next=null; 
          }
    Node(int data){
        this.data=data;
        this.next=null;
          }
}
public class MyClass{
    public static void main(String args[]) {
        Node head=new Node();
        Node temp=head;
        Scanner sc = new Scanner(System.in);
        int size=sc.nextInt();
        for(int i=1;i<=size;i++){
            temp.data=sc.nextInt();
            temp.next=new Node();
            temp=temp.next;
        }
        temp=null;
        while(head!=null){
            out.print(head.data+" ");
            head=head.next;
        }
    }
  }

Inputs: 5 1 2 3 4 5

Answer 1

The next pointer in the last node of a linked list should be null to denote that it is the last node.

In your case, you are keeping it 'not null'. In your for loop, just don't instantiate the next pointer if it is the last element you are reading.

    for(int i=1;i<=size;i++){
        temp.data=sc.nextInt();
        if(i != size) {
           temp.next=new Node();
           temp=temp.next;
        }
    }

Answer 2

You're creating the head-node outside of the loop and a new node within it.
You therefore get 1 extra node.

You might try the following:

public static void main(String args[]) {
    Node head=null;
    Node last=null;
    Scanner sc = new Scanner(System.in);
    int size=sc.nextInt();
    for(int i=1;i<=size;i++){
        if (head == null){
            head = new Node();
            last = head;
        } else {
            last.next = new Node();
            last = last.next();
        }
        last.data=sc.nextInt();
    }
    while(head!=null){
        out.print(head.data+" ");
        head=head.next;
    }
}

Answer 3

The problem is that even though you are setting temp=null after you exit your loop, you still have one extra unassigned node.

The simplest fix is to remove the '=' sign in your for loop so that you exit the loop after your last node and then assign your final value, like this:

    for(int i=1;i<size;i++){
        temp.data=sc.nextInt();
        temp.next=new Node();
        temp=temp.next;
    }
    temp.data=sc.nextInt();