题目：

题解：

struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2){
    int stack1[100];
    int stack2[100];
    int top1 = 0;
    int top2 = 0;
    int carry = 0;
    int sum = 0;
    struct ListNode* temp = NULL;
    struct ListNode* head = NULL;
    while (l1) {
        stack1[top1++] = l1->val;
        l1 = l1->next;
    }
    while (l2) {
        stack2[top2++] = l2->val;
        l2 = l2->next;
    }
    while (top1 || top2 || carry) {
        int m = top1 > 0 ? stack1[--top1] : 0;
        int n = top2 > 0 ? stack2[--top2] : 0;
        sum = m + n + carry;
        carry = sum / 10;
        head = malloc(sizeof(struct ListNode));
        head->val = sum % 10;
        head->next = temp;
        temp = head;
    }
    return head;
}