如何修复以下代码，以便获得输出的反向链表

Question

下面的代码是我尝试实现SinglyLinkedListNode和SinglyLinkedList类，并使用SinglyLinkedListNode reverse(SinglyLinkedListNode head)方法来反转这个链表。

输入由第一行组成，该行详细说明了测试用例的数量t。对于每个测试用例，第一行n表示链表中元素的数量。下一个n行数将分别包含该列表中的一个元素，这样输入如下：

1 (number of test cases)
5 (number of elements in list)
1 (element in list)
2 (element in list)
3 (element in list)
4 (element in list)
5 (element in list)

我如何修复以下代码，以便它可以打印这个反向链表，以便输出如下：

5 4 3 2 1

相反，我的代码打印出以下内容：

1
5
1
2
3
4
5
1 2 3 4 5 

我的代码：

import java.util.Scanner;
public class ReverseLinkedList {
static class SinglyLinkedListNode {
public int data;
public SinglyLinkedListNode next;
public SinglyLinkedListNode(int nodeData) {
data = nodeData;
next = null;
}
}
static class SinglyLinkedList {
private SinglyLinkedListNode head;
private SinglyLinkedListNode tail;
public SinglyLinkedList() {
SinglyLinkedListNode head = null;
SinglyLinkedListNode tail = null;
}
public void insertNode(int nodeData) {
SinglyLinkedListNode node = new SinglyLinkedListNode(nodeData);
if (this.head == null) {
this.head = node;
} else {
this.tail.next = node;
}
this.tail = node;
}
public SinglyLinkedListNode reverse(SinglyLinkedListNode head) {
SinglyLinkedListNode previous = null;
SinglyLinkedListNode current = head;
SinglyLinkedListNode next = null;
while (current != null) {
next = current.next;
current.next = previous;
previous = current;
current = next;
}
return previous;
}
public void printLinkedList() {
SinglyLinkedListNode node = head;
while (node != null) {
System.out.print(node.data + " ");
node = node.next;
}
}
}
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
SinglyLinkedList list = new SinglyLinkedList();
int testCases = input.nextInt();
if (testCases <= 10) {
input.nextLine();
int size = input.nextInt();
if (size <= 1000) {
for (int i = 0; i < size; i++) {
list.insertNode(input.nextInt());
}
list.reverse(list.tail);
list.printLinkedList();
}
}
}
}

Answer 1

use list.reverse(list.head)   

并将您的反向方法修改为

SinglyLinkedListNode previous = null; 
SinglyLinkedListNode current = head; 
SinglyLinkedListNode next = null; 
while (current != null) { 
next = current.next; 
current.next = previous; 
previous = current; 
current = next; 
} 
head= previous; 
return head;

同样在您的方法printLinkedList中设置

SinglyLinkedListNode node = tail; // instead of head

Answer 2

您应该将linkedlist的head而不是tail传递给reverse方法。

list.reverse(list.head);