**NOTE:** This problem is generated by LeetCode. TakeTheNotes has given only solution for educational purpose.

**Problem Name**: Add Two Numbers

**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 contains a single digit. Add the two numbers and return the sum as a linked list.

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

**Example 1:**

**Input**: l1 = [2,4,3], l2 = [5,6,4]
**Output**: [7,0,8]

**Example 2:**

**Input**: l1 = [2,4,3], l2 = [5,6,4]
**Output**: [7,0,8]

**Example 3:**

**Input**: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
**Output**: [8,9,9,9,0,0,0,1]

**Constraints:**

- The number of nodes in each linked list is in the range
`[1, 100]`

. `0 <= Node.val <= 9`

- It is guaranteed that the list represents a number that does not have leading zeros.

**Solution:**

```
struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2){
struct ListNode* retVal = (struct ListNode *)calloc(1, sizeof(struct ListNode));
if(retVal == NULL)
{
return NULL;
}
struct ListNode* head = retVal;
char carry = 0;
while(1)
{
int sum = 0;
if(l1 != NULL)
{
sum = l1->val;
l1 = l1->next;
}
if(l2 != NULL)
{
sum += l2->val;
l2 = l2->next;
}
sum += carry;
carry = sum/10;
retVal->val = sum%10;
if(l1 == NULL && l2 == NULL)
{
break;
}
retVal->next = (struct ListNode *)calloc(1, sizeof(struct ListNode));
if(retVal->next == NULL)
{
//not able to allocate memory. So returning
return head;
}
retVal = retVal->next;
}
if(carry)
{
retVal->next = (struct ListNode *)calloc(1, sizeof(struct ListNode));
if(retVal->next == NULL)
{
//not able to allocate memory. So returning
return head;
}
retVal = retVal->next;
retVal->val = carry;
}
return head;
}
```