2. Add Two Numbers

You are given two linked lists representing two non-negative numbers. 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.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     struct ListNode *next;
 * };
 */
struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) {
    struct ListNode* head = malloc(sizeof(struct ListNode));
    struct ListNode* current = head;
    int carry = 0;
    while(l1 && l2){
        current->next = malloc(sizeof(struct ListNode));
        current = current->next;
        current->val = l1->val + l2->val + carry;
        carry = current->val /10;
        current->val = (current->val)%10;
        l1 = l1->next;
        l2 = l2->next;
    }
    while(l1){
        current->next = malloc(sizeof(struct ListNode));
        current = current->next;
        current->val = l1->val + carry;
        carry = current->val /10;
        current->val = (current->val)%10;
        l1 = l1->next;
    }
    while(l2){
        current->next = malloc(sizeof(struct ListNode));
        current = current->next;
        current->val = l2->val + carry;
        carry = current->val /10;
        current->val = (current->val)%10;
        l2 = l2->next;
    }
    if(carry){
        current->next = malloc(sizeof(struct ListNode));
        current = current->next;
        current->val = carry;
    }
    current->next=NULL;
    return head->next;
}