Leetcode 2

/**
 * 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 *res = new ListNode(-1);
        ListNode *cur = res;
        int carry = 0;
        while (l1 || l2) {
            int n1 = l1 ? l1->val : 0;
            int n2 = l2 ? l2->val : 0;
            int sum = n1 + n2 + carry;
            carry = sum / 10;
            cur->next = new ListNode(sum % 10);
            cur = cur->next;
            if (l1) l1 = l1->next;
            if (l2) l2 = l2->next;
        }
        if (carry) cur->next = new ListNode(1);
        return res->next;

    }
};

我可能是个傻子，本来都给我逆序写好了，我偏要列表反转一下，mdzz

既然写了也要贴出来

ListNode* reverseList(ListNode *l){ 
        ListNode *res = l;
        ListNode *head = l->next;
        ListNode *cur = head;
        res->next = NULL;
                                       
        while(head){
            cur = head->next;
            head->next = res;
            res = head;
            head = cur;
        }
        return res;
    }

——