https://leetcode.com/submissions/detail/132382763/

addTwoNumbers.cpp

#include <iostream>


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

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
        ListNode *l3 = new ListNode(0);
        ListNode *currentl1 = l1;
        ListNode *currentl2 = l2;
        ListNode *currentl3 = l3;
        int carry = 0;
        for (int place = 0;; ++place) {
            int a = currentl1 == nullptr ? 0 : currentl1->val;
            int b = currentl2 == nullptr ? 0 : currentl2->val;
            int sum = a + b + carry;
            carry = (sum > 9) ? 1 : 0;
            currentl3->val = (sum > 9) ? sum-10 : sum;
            currentl1 = currentl1 == nullptr ? nullptr : currentl1->next;
            currentl2 = currentl2 == nullptr ? nullptr : currentl2->next;
            if (currentl1 != nullptr || currentl2 != nullptr) {
                currentl3->next = new ListNode(0);
                currentl3 = currentl3->next;
            } else if (carry) {
                currentl3->next = new ListNode(carry);
                break;
            } else {
                break;
            }
        }
        return l3;
    }
};

void printList(ListNode *list) {
    ListNode *tmp = list;
    std::cout << "(";
    while(tmp != nullptr) {
        std::cout << tmp->val;
        tmp = tmp->next;
        if (tmp != nullptr)
            std::cout << "->";
    }
    std::cout << ")";
}


int main () {
    int num1[3] = {2, 4, 3};
    int num2[4] = {5, 6, 4, 1};

    ListNode l1(num1[0]);
    ListNode *tmpl1 = &l1;
    for (int i = 0; i < 2; ++i) {
        tmpl1->next = new ListNode(num1[i+1]);
        tmpl1 = tmpl1->next;
    }

    ListNode l2(num2[0]);
    ListNode *tmpl2 = &l2;
    for (int i = 0; i < 2; ++i) {
        tmpl2->next = new ListNode(num2[i+1]);
        tmpl2 = tmpl2->next;
    }


    std::cout << "Input: ";
    printList(&l1);
    std::cout << " + ";
    printList(&l2);
    std::cout << std::endl;

    Solution solution;
    ListNode *result = solution.addTwoNumbers(&l1, &l2);

    std::cout << "Output: ";
    printList(result);
    std::cout << std::endl;

    return 0;
}