leetcode 2.Add Two Numbers

You are given two non-empty linked lists representing two non-negative integers. 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.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Example:

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.

思路：使用一个ListNode进行保存结果，进行一直后移链表操作

class Solution {
public:
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
        ListNode *res=new ListNode(0);
        ListNode *tmp=res;
        bool start=true;
        int num=0;
        while(l1||l2){
            if(l1) {
                num+=l1->val;
                l1=l1->next;
            }
            if(l2){
                num+=l2->val;
                l2=l2->next;
            }
            if(start) tmp->val=num%10;
            else {
                tmp->next=new ListNode(num%10);
                tmp=tmp->next;
            }
            start=false;
            num/=10;
        }
        if(num!=0) tmp->next=new ListNode(num);
        return res;
    }
};