[Algorithm] 38 week(10.17 ~ 10.23) 1/3

2. Add Two Numbers

var addTwoNumbers = function(l1, l2) {
    let result = new ListNode(0);
    let current = result;
    let carry = 0;

    while (l1 || l2 || carry) {
        let sum = carry;
        if (l1) {
            sum += l1.val;
            l1 = l1.next;
        }
        if (l2) {
            sum += l2.val;
            l2 = l2.next;
        }
        carry = Math.floor(sum / 10);
        current.next = new ListNode(sum % 10);

        current = current.next;
    }
    return result.next;
};