## Description

You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Example: Input: (2 -> 4 -> 3) + (5 -> 6 -> 4) Output: 7 -> 0 -> 8 Explanation: 342 + 465 = 807.

## Solution

This is a linkedlist question. For linkedlist question, we can use a dummy head for clear solution. It is not hard question. Just remember how iterate the linkedlist.

## Code

```
class Solution {
public:
ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
int carry = 0;
ListNode dummyHead(0);
ListNode* iter = &dummyHead; /*❶*/
while(carry || l1 || l2) { /*❷*/
if(l1){
carry += l1->val;
l1 = l1->next;
}
if(l2) {
carry += l2->val;
l2 = l2->next;
}
iter->next = new ListNode(carry%10);
iter = iter->next;
carry /= 10;
}
return dummyHead.next; /*❸*/
}
};
```

❶ use a dummy head.

❷ it is the template regarding to adding number with carry.

❸ return dummy head’s next.