Solution.cpp

/**
 * 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* res = new ListNode(0);
 ListNode* iter = res;
 int carry=0;
 while(l1 || l2 || carry) {
 int sum = 0;
 if (l1) { sum += l1->val; l1=l1->next; }
 if (l2) { sum += l2->val; l2=l2->next; }
 sum+=carry;
 carry=sum/10;
 sum=sum%10;
 ListNode* next = new ListNode(sum);
 iter->next = next;
 iter = iter->next;
 }
 return res->next;
 }
};