[LeetCode]2. Add Two Numbers

题目：

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：

就是模拟加法运算，注意进位就行了。

代码：

class Solution {public:ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {ListNode *root=NULL,*tan=NULL;int sum = 0;if (!l1 && !l2) return NULL;while (l1 || l2) {if (l1) {sum += l1->val;l1 = l1->next;}if (l2) {sum += l2->val;l2 = l2->next;}ListNode *p = new ListNode(sum % 10);if (root==NULL) {root = p;tan = p;}else {tan->next = p;tan = p;}sum = sum/10;}if (sum) {ListNode *p = new ListNode(sum % 10);tan->next = p;}return root;}};