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;

    }
}