/*
 * @lc app=leetcode id=2 lang=java
 *
 * [2] Add Two Numbers
 */

// @lc code=start
/**
 * 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 addTwoNumbers(ListNode l1, ListNode l2) {
        boolean propagated = false;
        ListNode r = null, cur = null;
        while(l1!=null ||l2!=null) {
            int v1 = l1!=null?l1.val:0;
            int v2 = l2!=null?l2.val:0;
            int v = v1 + v2 + (propagated?1:0);
            propagated = v/10!=0;
            v = v %10;
            // add node to result
            ListNode t = new ListNode(v);
            t.next = null;
            if(r == null) {
                r = t;
                cur = t;
            } else {
                cur.next = t;
                cur = cur.next;
            }

            if(l1!=null) {
                l1 = l1.next;
            }
            if(l2!=null) {
                l2 = l2.next;
            }
        }
        if(propagated) {
            ListNode t = new ListNode(1);
            t.next = null;
            cur.next = t;
            cur = cur.next;
        }
        return r;
    }
}
// @lc code=end