LeetCode HOT100 - 两数相加

本身就是直接模拟

主要是注意下链表的写法，比如设置一个哑节点以及如何避免末尾有多余节点之类

class Solution {
public:
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
        ListNode* dummy = new ListNode(0);
        auto cur = dummy;
        int flag = 0;
        while (l1 || l2 || flag) {
            int sum = flag;
            if (l1) {
                sum += l1->val;
                l1 = l1->next;
            }
            if (l2) {
                sum += l2->val;
                l2 = l2->next;
            }
            flag = sum / 10;
            cur->next = new ListNode(sum % 10);
            cur = cur->next;
        }
        return dummy->next;
    }
};