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

鏈表操作，相當於高精度

/**
 * 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 *head,*p,*s;
       head=(ListNode*)malloc(sizeof(ListNode));
       p=head;
       int a,a1,a2,a3;
       int tmp=0;
       while(1){
           if(l1!=NULL)  a1=l1->val;
           else          a1=0;
           if(l2!=NULL)  a2=l2->val;
           else          a2=0;
           a3=a1+a2+tmp;
           a=a3%10;
           tmp=a3/10;
           s=(ListNode*)malloc(sizeof(ListNode));
           s->val=a;
           p->next=s;
           p=s;
           if(l1!=NULL)  l1=l1->next;
           if(l2!=NULL)  l2=l2->next;
           if(l1==NULL && l2==NULL && tmp==0)
            break;
       }
       head=head->next;
       p->next=NULL;
       
       return (head);
       
    }
};