Problem Description： You are given two non-empty linked lists representing two non-negative integers. 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. You may assume the two numbers do not contain any leading zero, except the number 0 itself.
Examples: Input: (2 -> 4 -> 3) + (5 -> 6 -> 4) Output: 7 -> 0 -> 8 Explanation: 342 + 465 = 807.
Solution:
/** * 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) { if (l1 == NULL || l2 == NULL) { return l1 == NULL ? l2:l1; } int value = l1->val +l2->val; l1 = l1->next; l2 = l2->next; ListNode* sum = new ListNode(value % 10); sum->next = addTwoNumbers(l1, l2); if (value >= 10) { sum->next = addTwoNumbers(new ListNode(value / 10), sum->next); } return sum; } };