Add TwoNumbers 两个链表相加

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.

这道题需要注意下进位

struct ListNode {
      int val;
      ListNode *next;
      ListNode(int x) : val(x), next(NULL) {}
  };

class Solution {
public:
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
        if (l1==NULL)
            return l2;
        if (l2==NULL)
            return l1;
        ListNode* res = new ListNode((l1->val+l2->val)%10);
        ListNode* pNode = res;
        int carry = (l1->val+l2->val)/10;
        while (l1->next || l2->next || carry)
        {
            int v1=0,v2 = 0;
            if (l1->next)
            {
                v1 = l1->next->val;
                l1 = l1->next;
            }
            if (l2->next)
            {
                v2 = l2->next->val;
                l2 = l2->next;
            }
            ListNode* node = new ListNode((v1+v2+carry)%10);
            carry = (v1+v2+carry)/10;
            pNode->next = node;
            pNode = node;
        }
        return res;
    }
};
 
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