ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {

// Start typing your C/C++ solution below

// DO NOT write int main() function

int carry = 0;

ListNode *list = new ListNode(0);

ListNode *head = list;

ListNode *prev = list;

while (l1 && l2) {

carry += l1->val + l2->val;

list = new ListNode(0);

list->val = carry % 10;

carry /= 10;

l1 = l1->next;

l2 = l2->next;

prev->next = list;

prev = prev->next;

}

while (l1) {

carry += l1->val;

list = new ListNode(0);

list->val = carry % 10;

carry /= 10;

l1 = l1->next;

prev->next = list;

prev = prev->next;

}

while (l2) {

carry += l2->val;

list = new ListNode(0);

list->val = carry % 10;

carry /= 10;

l2 = l2->next;

prev->next = list;

prev = prev->next;

}

if (carry) {

list = new ListNode(0);

list->val = carry;

prev->next = list;

prev = prev->next;

}

return head->next;

}