# Leet code | Problem 2: Add Two Numbers

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

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;
}

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
}

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