[LintCode] Add Two Numbers 两个数字相加

You have two numbers represented by a linked list, where each node contains a single digit. The digits are stored in

reverse

order, such that the 1's digit is at the head of the list. Write a function that adds the two numbers and returns the sum as a linked list.

Have you met this question in a real interview?

Yes

Example

Given

7->1->6 + 5->9->2

. That is,

617 + 295

.

Return

2->1->9

. That is

912

.

Given

3->1->5

and

5->9->2

, return

8->0->8

.

LeetCode上的原题，请参见我之前的博客Add Two Numbers。

class Solution {
public:
/**
* @param l1: the first list
* @param l2: the second list
* @return: the sum list of l1 and l2
*/
ListNode *addLists(ListNode *l1, ListNode *l2) {
ListNode *dummy = new ListNode(-1), *cur = dummy;
int carry = 0;
while (l1 || l2) {
int num1 = l1 ? l1->val : 0;
int num2 = l2 ? l2->val : 0;
int sum = num1 + num2 + carry;
cur->next = new ListNode(sum % 10);
carry = sum / 10;
if (l1) l1 = l1->next;
if (l2) l2 = l2->next;
cur = cur->next;
}
if (carry) cur->next = new ListNode(1);
return dummy->next;
}
};