好久没有写C了，LeetCode上面的一道题：

You are given two non-empty linked lists representing two non-negative

1. The digits are stored in reverse order and each of their

2. 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.

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

struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) {

    struct ListNode* result = (struct ListNode*)malloc(sizeof(struct ListNode));
    result->next = NULL;
    struct ListNode* result_temp = result;
    struct ListNode* l1_node;
    struct ListNode* l2_node;

    l1_node = l1;
    l2_node = l2;

    while (l1_node != NULL || l2_node != NULL)
    {
        struct ListNode* result_node = (struct ListNode*)malloc(sizeof(struct ListNode));
        result_node->val = 0;
        result_node->next = NULL;
        if (l1_node != NULL)
        {
            result_node->val += l1_node->val;
            l1_node = l1_node->next;
        }
        if (l2_node != NULL)
        {
            result_node->val += l2_node->val;
            l2_node = l2_node->next;
        }
        while (result_temp->next!= NULL)
        {
            result_temp = result_temp->next;
        }
        result_temp->next = result_node;
    }

    result_temp = result->next;
    while (result_temp != NULL)
    {
        if (result_temp->val >= 10)
        {
            if (result_temp->next != NULL)
            {
                result_temp->next->val++;
            }
            else
            {
                struct ListNode* last_node = (struct ListNode*)malloc(sizeof(struct ListNode));
                last_node->val = 1;
                last_node->next = NULL;
                result_temp->next = last_node;
            }
            result_temp->val = result_temp->val - 10;
        }
        result_temp = result_temp->next;
    }
    return result->next;    
}

对比下大神写的代码（C++）：

ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
    ListNode preHead(0), *p = &preHead;
    int extra = 0;
    while (l1 || l2 || extra) {
        int sum = (l1 ? l1->val : 0) + (l2 ? l2->val : 0) + extra;
        extra = sum / 10;
        p->next = new ListNode(sum % 10);
        p = p->next;
        l1 = l1 ? l1->next : l1;
        l2 = l2 ? l2->next : l2;
    }
    return preHead.next;
}