leetcode 2. add two numbers

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

Solution:

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public class  {
public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
ListNode r = new ListNode(0);
ListNode h = r;
ListNode beforeend = r;

while(l1 != null && l2!= null){
r.val += l1.val + l2.val;

r.next = new ListNode(r.val / 10);
r.val %= 10;

beforeend = r;
r = r.next;
l1 = l1.next;
l2 = l2.next;
}

ListNode rest;
if (l1 == null) rest = l2; else rest =l1;

while(rest != null){
r.val += rest.val;

r.next = new ListNode(r.val / 10);
r.val %= 10;

beforeend = r;
r = r.next;
rest = rest.nest;
}
if(beforeend.next != null && beforeend.next.val == 0) beforeend.next=null;

return h;
}
}