LeetCode:Add Two Numbers

问题：

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

思路：

如果都不为空，则相加，相加超过10则进位。如果是尾节点，则增加一个节点。

代码：

/** * 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 * ret = new ListNode(0);        ListNode *p = ret;        int sum = 0;        while(1){            if(l1 != NULL){                sum += l1 -> val;                l1 = l1 -> next;            }            if(l2 != NULL){                sum += l2 -> val;                l2 = l2 -> next;            }            p -> val = sum % 10;            sum /= 10;            if(l1 != NULL || l2 != NULL | sum )                p = (p -> next = new ListNode(0));            else                 break;        }        return ret;    }};