LeetCode 2.Add Two Numbers(链表)

• 先声明一个链表指针l1，在声明一个链表指针l2, 用l1来维护他们的和，l2记录l1的初始位置。

/**
 * 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* l3 = new ListNode(0);
        ListNode* l4 = l3;
        int res = 0;
        while(l1 || l2){
            l3->val += res;
            res = 0;
            
            if(l1)
                l3->val += l1->val, l1 = l1->next;
            if(l2)
                l3->val += l2->val, l2 = l2->next;
            if(l3->val > 9)
                res += (l3->val) / 10, l3->val = (l3->val) % 10;
            if((l1 || l2) == false){
                if(res != 0){
                    l3->next = new ListNode(0);
                    l3 = l3->next;
                    l3->val += res;
                }
                break;
            }
            l3->next = new ListNode(0);
            l3 = l3->next;
        }
        return l4;
    }
};