Difficulty: Medium

Add Two Numbers: 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.

Input: l1 = [2->4->3] + l2 = [5->6->4]

Output: [7,0,8]

Explanation: 342 + 465 = 807.

## Python Solution

``````class Solution:
def insert(self,l,v):
if l==None:
l.val=v
else:
r=l
while r.next!=None:
r=r.next
tmp=ListNode(v)
r.next=tmp
res=ListNode(0)
s,s2='',''
while l1!=None:
s+=str(l1.val)
l1=l1.next
while l2!=None:
s2+=str(l2.val)
l2=l2.next
s=int(s[::-1])+int(s2[::-1])
for x in str(s)[::-1]:
self.insert(res,int(x))
return res.next``````

## Java Solution

``````public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
int carry = 0, sum;
ListNode ln1 = l1, ln2 = l2, node = head;

while (carry != 0 || ln1 != null || ln2 != null) {
sum = carry; // reset sum to value of carry

if (ln1 != null) {
sum += ln1.val;
ln1 = ln1.next;
}
if (ln2 != null) {
sum += ln2.val;
ln2 = ln2.next;
}

carry = sum / 10;
node.next = new ListNode(sum % 10);
node = node.next;
}
}``````

## C Solution

``````struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2){
struct ListNode *p = l1, *q = l2;
struct ListNode *result = NULL, *curr = NULL;
int carry = 0;
while (p != NULL || q != NULL || carry != 0) {
struct ListNode* newNode = (struct ListNode*)malloc(sizeof(struct ListNode));
int x = (p != NULL) ? p->val : 0;
int y = (q != NULL) ? q->val : 0;
int sum = (carry + x + y) % 10;
carry = (carry + x + y) / 10;
newNode->val = sum;
newNode->next = NULL;
if (result == NULL) {
result = curr = newNode;
} else {
curr->next = newNode;
curr = newNode;
}
if (p != NULL) p = p->next;
if (q != NULL) q = q->next;
}
return result;
}
``````

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