/** You are given two linked lists representing two non-negative numbers. 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. Input: (2 -> 4 -> 3) + (5 -> 6 -> 4) Output: 7 -> 0 -> 8 */ /** * 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 dummy(0); ListNode* head = &dummy; ListNode* res = head; ListNode* p1 = l1; ListNode* p2 = l2; int carry = 0; while (l1 && l2) { int sum = l1->val + l2->val + carry; res->next = new ListNode(sum%10); carry = sum/10; l1 = l1->next; l2 = l2->next; res = res->next; } while (l1) { int sum = l1->val + carry; res->next = new ListNode(sum%10); carry = sum /10; res = res->next; l1 =l1->next; } while (l2) { int sum = l2->val + carry; res->next = new ListNode(sum%10); carry = sum/10; res = res->next; l2 = l2->next; } //be careful of carrying if (carry >0) { res->next = new ListNode(carry); } return head->next; } };