# 2. Add Two Numbers (Medium)

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.
```

## Solutions

``````class Solution {

public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
ListNode ans = null;
ListNode ptr = null;

int carry = 0;
while (l1 != null || l2 != null) {
int x1 = 0;
int x2 = 0;

if (l1 != null) {
x1 = l1.val;
l1 = l1.next;
}

if (l2 != null) {
x2 = l2.val;
l2 = l2.next;
}

int sum = (x1 + x2 + carry);
ListNode x = new ListNode(sum % 10);
if (ans == null) {
ans = x;
ptr = ans;
} else {
ptr.next = x;
ptr = ptr.next;
}
carry = sum / 10;
}

// Don't forget to take account of the last carry which may not be 0
if (carry != 0) {
ptr.next = new ListNode(1);
}

return ans;
}
}
``````