// Source : https://leetcode.com/problems/add-two-numbers/

// Author : Han Zichi

// Date : 2015-08-12

/**

* Definition for singly-linked list.

* function ListNode(val) {

* this.val = val;

* this.next = null;

* }

*/

/**

* @param {ListNode} l1

* @param {ListNode} l2

* @return {ListNode}

*/

var addTwoNumbers = function(l1, l2) {

var add = 0

, ans

, head;

while(l1 || l2) {

var a = l1 ? l1.val : 0

, b = l2 ? l2.val : 0;

var sum = a + b + add;

add = ~~(sum / 10);

var node = new ListNode(sum % 10);

if (!ans)

ans = head = node;

else {

head.next = node;

head = node;

}

if (l1)

l1 = l1.next;

if (l2)

l2 = l2.next;

}

if (add) {

var node = new ListNode(add);

head.next = node;

head = node;

}

return ans;

};