反转链表

题目描述

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 Solution {
   
    public ListNode ReverseList(ListNode head) {
        ListNode lastNode = null, p = head, nextNode;
        if (head == null) return null;
        
        for (;p.next != null; p = nextNode) {
            nextNode = p.next;
            p.next = lastNode;
            lastNode = p;
            
        }
        p.next = lastNode;
        return p;
    }
}