反转链表：从创建到反转，讲清链表

链表的节点数据结构：

package cn.yaunsine.domain;/*** 链表节点数据结构*/
public class ListNode {/*** 元素值*/public int val;/*** 指向下一个节点的指针*/public ListNode next;public ListNode (int val) {this.val = val;this.next = null;}
}

创建链表，反转链表，打印反转前后的链表

import cn.yaunsine.domain.ListNode;
import org.junit.Test;/*** 反转链表* @author yaunsine*/
public class ReverseListNode {/*** 打印链表* @param root 头节点*/private void print(ListNode root) {ListNode node = root;while (node != null) {System.out.print(node.val);node = node.next;}System.out.println();}/*** 反转链表* @param node 翻转前的头节点* @return 反转后的头节点*/ListNode reverse(ListNode node) {if (node == null || node.next == null) {return node;}ListNode tail = reverse(node.next);node.next.next = node;node.next = null;return tail;}/*** 把数组转为链表* @param nums 数组* @return 链表*/ListNode createListNode(int[] nums) {ListNode head = new ListNode(-1);ListNode tail = head;for (int i = 0; i < nums.length; i++) {ListNode node = new ListNode(nums[i]);tail.next = node;tail = tail.next;}return head.next;}/*** 测试方法*/@Testpublic void testNode() {int[] nums = {3, 8, 2, 1, 5, 4};ListNode head = createListNode(nums);print(head);head = reverse(head);print(head);}
}