题解 | 反转链表

import java.util.*;

/*
 * public class ListNode {
 *   int val;
 *   ListNode next = null;
 *   public ListNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {

    public ListNode ReverseList (ListNode head) {
        // write code here
      if(head==null||head.next==null){
        return head;
      }
      ListNode pre = null,cur = head;
      while(cur!=null){
        ListNode next = cur.next;
        cur.next = pre;
        pre = cur;
        cur = next;
      }
      return pre;
    }
}