LeetCode2. Add Two Numbers

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

这个题跟67. Add Binary 思路是一样的
设置一个flag表示进位，一个da表示当前位所置的数字。
最后如果有进位，则增加一个节点。

class Solution {public:    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {        int flag=0,da=0;        ListNode *L;        ListNode *s,*r;        L  = new ListNode(0);        r = L;        ListNode *p1,*p2;        p1 = l1;        p2 = l2;        for(p1,p2;p1!=NULL && p2!=NULL;p1 = p1->next,p2 = p2->next)        {            int temp = (p1->val + p2->val+ flag);                flag = temp / 10 ;                da = temp % 10;                s = new ListNode(da);                r->next = s;                r = s;        }        while(p1!= NULL)        {            int temp = (p1->val+ flag);                flag = temp / 10 ;                da = temp % 10;                s = new ListNode(da);                r->next = s;                r = s;                p1 = p1->next;        }        while(p2!= NULL)        {            int temp = (p2->val+ flag);            flag = temp / 10 ;            da = temp % 10;            s = new ListNode(da);            r->next = s;            r = s;            p2 = p2->next;        }        if (flag == 1)        {            s = new ListNode(flag);            r->next = s;            r = s;        }        r->next = NULL;        return L->next;    }};