[leetcode] Add Two Numbers *

/*
 * Easy
 *
 * @author: HZT
 * @date: 2013-3-7
 */

#include <iostream>
using namespace std;

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
        if(!l1) return l2;
        if(!l2) return l1;

        ListNode* ans = NULL;
        ListNode* tail = new ListNode(0);
        int carry = 0;

        while(true){
            int val = (l1->val + l2->val + carry) % 10;
            carry = (l1->val + l2->val + carry) / 10;

            tail->next = new ListNode(val);
            tail = tail->next;
            if(!ans) ans = tail;

            l1 = l1->next;
            l2 = l2->next;

            if(!l1 || !l2){
                if(!l2) l2 = l1;
                while(l2){
                    int val = (l2->val + carry) % 10;
                    carry = (l2->val + carry) / 10;

                    tail->next = new ListNode(val);
                    tail = tail->next;
                    if(!ans) ans = tail;

                    l2 = l2->next;
                }

                if(carry){
                    tail->next = new ListNode(carry);
                    tail = tail->next;
                    if(!ans) ans = tail;
                }

                break;
            }
        }

        return ans;
    }
};

int main(){
    Solution* s = new Solution();

    ListNode* l1 = new ListNode(9);
    ListNode* l2 = new ListNode(9);

    ListNode* ans = s->addTwoNumbers(l1, l2);
    while(ans){
        cout << ans->val;
        ans = ans->next;
    }

    return 0;
}