[Leetcode] Add Two Number

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

[解题思路]

题目很简单，我讲几种情况都压缩在一起判断了，比较简洁

[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* head = NULL;
ListNode** pp = &head;

ListNode* p1 = l1;
ListNode* p2 = l2;
int carry = 0;
while (p1 || p2 || carry) {
int p1Val = (p1 ? p1->val : 0);
int p2Val = (p2 ? p2->val : 0);
int temp = p1Val + p2Val + carry;
carry = temp / 10;
*pp = new ListNode(temp % 10);
pp = &(*pp)->next;
if (p1) p1 = p1->next;
if (p2) p2 = p2->next;
}

return head;
}
};