leetCode-206:Reverse Linked List

问题描述

给定一个链表，要求将其反转。题目链接：**点我**

样例输入输出

输入：1->2->3->4->5

输出：5->4->3->2->1

输入：1

输出：1

问题解法

此题很明确，也没什么算法，直接反转即可。代码如下

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution
{
    public ListNode reverseList(ListNode head)
    {
        if (head == null)
        {
            return head;
        }
        
        ListNode dummy = new ListNode(-1, head);
        while (head.next != null)
        {
            ListNode p = dummy.next;
            dummy.next = head.next;
            head.next = head.next.next;
            dummy.next.next = p;
        }
        
        return dummy.next;
    }
}