用一个变量记录进位。
//2. Add Two Numbers
/**
* 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 *p1=l1,*p2=l2,*head=new ListNode(0),*p=head;
int carry=0;
while(p1||p2)
{
int val1=0,val2=0;
if(p1)
{
val1=p1->val;
p1=p1->next;
}
if(p2)
{
val2=p2->val;
p2=p2->next;
}
int tmp=carry+val1+val2;
p->next=new ListNode(tmp%10);
carry=tmp/10;
p=p->next;
}
if(carry!=0)
{
p->next=new ListNode(carry);
}
return head->next;
}
};