Add Two Numbers

class Solution
{
public:
ListNode *addTwoNumbers(ListNode *l1, ListNode *l2)
{
ListNode *ans=NULL;
int t=0;//进位
ListNode * ret=NULL;
while(l1&&l2)
{
ListNode * tNode = new ListNode((l1->val+l2->val+t)%10);
if(ans == NULL)
{
ans=tNode;
ret=ans;
}
else
{
ans->next=tNode;
ans=ans->next;
}
t=(l1->val+l2->val+t)/10;
l1=l1->next;
l2=l2->next;
}
ListNode * l=l1==NULL?l2:l1;
while(l)
{
ListNode * tNode = new ListNode((l->val+t)%10);
if(ans == NULL)
{
ans=tNode;
ret=ans;
}
else
{
ans->next=tNode;
ans=ans->next;
}
t=(l->val+t)/10;
l=l->next;
}
if(t!=0)
{
ListNode * tNode = new ListNode(t);
if(ans == NULL)
{
ans=tNode;
ret=ans;
}
else
{
ans->next=tNode;
ans=ans->next;
}
}
return ret;
}
};