leet2.cpp

/*
http://leetcode.com/onlinejudge#question_2
*/
/**
 * 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) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        ListNode* tl = new ListNode(-1);
        ListNode* ans = tl;
        tl->next = NULL;
        int sum = 0,
        cry = 0;
        bool firstnum = true;
        
        while (l1 || l2)
        {

                sum = cry;
                if (l1)
                {
                    sum += l1->val;
                    l1 = l1->next;
                }
                    
                if (l2)
                {
                     sum += l2->val;
                     l2 = l2->next;
                }
                   
                cry = sum / 10;
                sum = sum % 10;
                
                /* first num*/
                if (firstnum)
                {
                    tl->val = sum;
                    firstnum = false;
                }
                else
                {
                    ListNode* tmp = new ListNode(sum);
                    tl->next= tmp;
                    tl = tmp;
                }

        }
        /* last cry */
        if (cry)
        {
            ListNode* tmp = new ListNode(cry);
            tmp->next = NULL;
            tl->next = tmp;      
        }


        return ans;
        
    }
};