#include <cstdint>

namespace {

struct ListNode {
    int val;
    ListNode *next;
    ListNode() : val(0), next(nullptr) {}
    ListNode(int x) : val(x), next(nullptr) {}
    ListNode(int x, ListNode *next) : val(x), next(next) {}
};

class Solution {
    auto getNum(ListNode* l1, ListNode* l2) -> ListNode* {
        ListNode *head, *prev, *curr;

        int v_ume = 0;

        while (l1 || l2) {
            int a = 0, b = 0;
            if (l1) {
                a = l1->val;
                l1 = l1->next;
            }
            if (l2) {
                b = l2->val;
                l2 = l2->next;
            }

            int sum = a + b + v_ume;

            int x = sum % 10;
            v_ume = sum / 10;

            curr = new ListNode(x);
            if (!head) {
                head = curr;
            } else {
                prev->next = curr;
            }
            prev = curr;
        }

        if (v_ume != 0) {
            curr = new ListNode(v_ume);
            prev->next = curr;
        }

        return head;
    }
   
public:
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
        return getNum(l1, l2);
    }
};

}

#include <gtest/gtest.h>

TEST(P2, 1) {
    Solution s;
    auto res = s.addTwoNumbers(nullptr, nullptr);
}