题目

原题在此
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 contains a single digit. Add the two numbers and return the sum as a linked list.
You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Example 1:
Input: l1 = [2,4,3], l2 = [5,6,4]
Output: [7,0,8]
Explanation: 342 + 465 = 807.

Example 2:
Input: l1 = [0], l2 = [0]
Output: [0]

Example 3:
Input: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
Output: [8,9,9,9,0,0,0,1]

Constraints:

The number of nodes in each linked list is in the range [1, 100].
0 $\leq$ Node.val $\leq$ 9
It is guaranteed that the list represents a number that does not have leading zeros.

解析

没啥好讲的, 按照题意做就好. 就相加, 进位.

代码

C++

/**
 * 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) {
        int val = 0;
        ListNode* holder = new ListNode(0);
        ListNode* onWork = holder;
        
        while(l1 || l2 || val){
            val += (l1 ? l1->val : 0);
            val += (l2 ? l2->val : 0);
            l1 = (l1 ? l1->next : l1);
            l2 = (l2 ? l2->next : l2);
            ListNode* node = new ListNode(val%10);
            val = val / 10;
            onWork->next = node;
            onWork = onWork->next;
        }
        return holder->next;
    }
};