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
模拟加法，注意最后加法结束时可能有进位需要处理一下。
/** * 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) { // Start typing your C/C++ solution below // DO NOT write int main() function if (l1 == NULL && l2 == NULL) return NULL; ListNode *head = NULL; ListNode *pre = NULL; int flag = 0; while(l1 && l2) { ListNode *node = new ListNode(l1->val + l2->val + flag); flag = node->val / 10; node->val %= 10; if (head == NULL) head = node; else pre->next = node; pre = node; l1 = l1->next; l2 = l2->next; } while(l1) { ListNode *node = new ListNode(l1->val + flag); flag = node->val / 10; node->val %= 10; if (head == NULL) head = node; else pre->next = node; pre = node; l1 = l1->next; } while(l2) { ListNode *node = new ListNode(l2->val + flag); flag = node->val / 10; node->val %= 10; if (head == NULL) head = node; else pre->next = node; pre = node; l2 = l2->next; } if (flag > 0) { ListNode *node = new ListNode(flag); pre->next = node; } return head; }};