leetcode-2-链表题-两数相加

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题目

微信截图_20200310195742.png

解法

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/**
 * 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) {
        if(!l1) return l2;
        if(!l2) return l1;

        ListNode *res = new ListNode(-1);
        ListNode *tmpRes = res;
        int temp = 0;  // 进位
        while(l1 || l2 || temp){
            int sum = temp;

            if(l1){
                sum += l1->val;
                l1 = l1->next;
            }

            if(l2){
                sum += l2->val;
                l2 = l2->next;
            }

            tmpRes->next = new ListNode(sum % 10);
            tmpRes = tmpRes->next;
            temp = sum / 10;
        }

        return res->next;
    }
};