反转链表_JAVA

 package algorithms;

 /*
  *
  *
  *     输入一个链表，反转链表后，输出新链表的表头。
  *
     public class ListNode {
         int val;
         ListNode next = null;

         ListNode(int val) {
             this.val = val;
         }
     }

 */

 public class ReverseList {
     public ListNode ReverseList_1(ListNode head) {
         ListNode pReverseNodeHead = null;
         ListNode pNode = head;
         ListNode pPrevious = null;
         while(pNode!=null) {
             ListNode pNext = pNode.next;   //将下一个节点保存起来
             if(pNext==null)
                 pReverseNodeHead = pNode;
             pNode.next = pPrevious;
             pPrevious = pNode;
             pNode = pNext;            //定义了几个指针 移动的时候要注意一起移动

         }
         return pReverseNodeHead;

     }
 }