翻转链表

/**

• Definition for ListNode.
• public class ListNode {
• int val;
• ListNode next;
• ListNode(int val) {
• this.val = val;
• this.next = null;
• }
• }
  /
  public class Solution {
  /*
  • @param head: The head of linked list.
  • @return: The new head of reversed linked list.
    */
    public ListNode reverse(ListNode head){
    // write your code here
    if (head == null || head.next == null)
    return head;
    ListNode second = head.next;
    head.next = null;
    ListNode res = reverse(second);
    second.next = head;
    return res;
    }
    }