leetcode Add Two Numbers c#版本

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

话不多说，直接上代码

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication2
{
     public class ListNode {
     public int val;
     public ListNode next;
     public ListNode(int x) { val = x; }
 }


    public class Solution
    {
        public Solution()
        {
        }

        public ListNode AddTwoNumbers(ListNode l1, ListNode l2)
        {
            ListNode rev1 = ReverseList(l1);
            ListNode rev2 = ReverseList(l2);
            ListNode head, last;
            ListNode param1, param2;
            param1 = rev1;
            param2 = rev2;
            head = last = null;
            while (param1 != null || param2 != null)
            {
                ListNode cur = new ListNode(0);
                if (param1 != null)
                {
                    cur.val += param1.val;
                    param1 = param1.next;
                }
                if (param2 != null)
                {
                    cur.val += param2.val;
                    param2 = param2.next;
                }
                if (last == null)
                {
                    last = head = cur;
                }
                else
                {
                    last.next = cur;
                    last = cur;
                }
            }
            ListNode ret = ReverseList(head);
            return ret;
        }
        ListNode ReverseList(ListNode ori)
        {
            ListNode cur, next, afterNext, ret;
            ret = null;
            cur = ori;
            next = cur.next;
            afterNext = null;
            while (true)
            {
                if (GetNextTwo(cur, ref next, ref afterNext))
                {
                    next.next = cur;
                    cur = next;

                    next = afterNext;
                    afterNext = next.next;

                }
                else
                {
                    if (next == null)
                    {
                        break;
                    }
                    else if (afterNext == null)
                    {
                        next.next = cur;
                        ret = next;
                        break;
                    }
                }
            }
            ori.next = null;
            return ret;
        }
        bool GetNextTwo(ListNode head, ref ListNode next, ref ListNode afterNext)
        {
            bool haveNextTwo = false;
            if (null == next && null != head.next)
            {
                next = head.next;
            }
            if (null != next.next)
            {
                afterNext = next.next;
                haveNextTwo = true;
            }
            return haveNextTwo;
        }
    }

}