LeetCode题解：Add Two Numbers

Add Two Numbers

You are given two linked lists representing two non-negative numbers. 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.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)

Output: 7 -> 0 -> 8
思路：
中小学竞赛题。
题解：

/**
* 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* i1 = l1;
ListNode* i2 = l2;

ListNode* ret = new ListNode(0);
ListNode* ret_last = ret;

bool carry = false;

while(i1 != nullptr || i2 != nullptr)
{
int s = 0;

if (i1 != nullptr)
s = i1->val, i1 = i1->next;

if (i2 != nullptr)
s += i2->val, i2 = i2->next;

s += carry;

ret_last->next = new ListNode(s % 10);
ret_last = ret_last->next;

carry = (s >= 10);
}

if (carry)
ret_last->next = new ListNode(1);

ret_last = ret->next;
delete ret;

return ret_last;
}
};