/**
* Definition for singly-linked list.
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) { val = x; }
* }
*/
class Solution {
public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
Stack s1 = new Stack<>();
Stack s2 = new Stack<>();
while(l1 != null)
{
s1.push(l1.val);
l1 = l1.next;
}
while(l2 != null)
{
s2.push(l2.val);
l2 = l2.next;
}
ListNode result = new ListNode(0);
int sum = 0;
while(!s1.isEmpty() || !s2.isEmpty())
{
if(!s1.isEmpty()) sum += s1.pop();
if(!s2.isEmpty()) sum += s2.pop();
result.val = sum%10;
ListNode cur = new ListNode(sum/10);
cur.next = result;
result = cur;
sum /= 10;
}
return result.val == 0? result.next:result;
}
}