Merge Two Sorted Lists

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first
two lists.struct ListNode {
int val;
ListNode *next;
ListNode(int x) : val(x), next(NULL) {}
};

ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
ListNode *helper=new ListNode(0);
ListNode *head=helper;
while(l1 && l2){
if(l1->val< l2->val){
helper->next=l1;
l1=l1->next;
}
else{
helper->next=l2;
l2=l2->next;
}
helper=helper->next;
}
if(l1)
helper->next=l1;
if(l2)
helper->next=l2;
return head->next;
}