# Why am i getting a runtime error?

• ``````class Solution {
public:
ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
if(l1==NULL && l2!=NULL)
return l2;
if(l1!=NULL && l2==NULL)
return l1;
if(l1==NULL && l2==NULL)
return NULL;
ListNode* start=(ListNode*)malloc(sizeof(ListNode));
ListNode* temp=start;
int sum=0;
int carry=0;
while(l1!=NULL && l2!=NULL)
{
sum=(l1->val+l2->val+carry)%10;
carry=(l1->val+l2->val+carry)/10;
start->val=sum;
start->next=(ListNode*)malloc(sizeof(ListNode));
l1=l1->next;
l2=l2->next;
start=start->next;
}
while(l1!=NULL)
{
sum=(l1->val+carry)%10;
carry=(l1->val+carry)/10;
start->val=sum;
start->next=(ListNode*)malloc(sizeof(ListNode));
l1=l1->next;
start=start->next;
}
while(l2!=NULL)
{
sum=(l2->val+carry)%10;
carry=(l2->val+carry)/10;
start->val=sum;
start->next=(ListNode*)malloc(sizeof(ListNode));
l2=l2->next;
start=start->next;
}
if(carry!=0)
{
start->val=carry;
start->next=NULL;
return temp;
}
else
{
ListNode* t=temp;
while(temp->next->next!=NULL)
temp=temp->next;
temp->next=NULL;
return t;
}

}
};``````

• ctrl+k when input code : )

• You are missing brackets in third if statement. Add that and see if it still gets error.

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