# 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

两个链表相加的问题,需要处理好进位就成了,比较简单,直接上代码:

```c++
class Solution {
public:
ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {
ListNode dummy(0);
ListNode* p = &dummy;

int cn = 0;

while(l1 || l2) {
int val = cn + (l1 ? l1->val : 0) + (l2 ? l2->val : 0);
cn = val / 10;
val = val % 10;
p->next = new ListNode(val);
p = p->next;
if(l1) {
l1 = l1->next;
}
if(l2) {
l2 = l2->next;
}
}

if(cn != 0) {
p->next = new ListNode(cn);
p = p->next;
}

return dummy.next;
}
};
```