Add Two Numbers创建list和两个list相加

You are given two non-empty linked lists representing two non-negative integers. 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.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

class Solution {public:    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2)    {        ListNode preHead(0),*p=&preHead;        int extra = 0;        while (l1||l2||extra)        {            int sum = (l1 ? l1->val : 0) + (l2 ? l2->val : 0) + extra;            extra = sum / 10;            p->next = new ListNode(sum % 10);            p = p->next;            l1 = l1 ? l1->next : l1;            l2 = l2 ? l2->next : l2;        }        return preHead.next;    }    ListNode* createList(int *nums, int size)    {        ListNode preHead(0), *p = &preHead;        for (int i = 0; i < size; i++)        {            p->next = new ListNode(nums[i]);            p = p->next;        }        return preHead.next;    }};