Add Two Numbers

问题描述：

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 contain a single digit. Add the two numbers and return it as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Example:

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.

解决方法：

同时利用两个队列各自对应的位置相加：

代码描述：

 

 

/**
 * 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 == nullptr) return l2;
        if (l2 == nullptr) return l1;
        
        ListNode *res = new ListNode(-1);
        ListNode *one = l1, *two = l2, *cur = res;
        
        int carry = 0;
        while (one || two || carry) {
            int sum = carry;
            
            if (one) {
                sum += one->val;
                one = one->next;
            }
            
            if (two) {
                sum += two->val;
                two = two->next;
            }
            
            cur->next = new ListNode(sum % 10);
            carry = sum / 10;
            
            cur = cur->next;
        }
        
        return res->next;
    }
    
};