similar to merge sort
class Solution {
public:
ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
ListNode *head=new ListNode(0),*cur;
cur=head;
ListNode *cur1=l1,*cur2=l2;
while(cur1!=NULL&&cur2!=NULL){
if(cur1->val<cur2->val){
cur->next=cur1;
cur=cur->next;
cur1=cur1->next;
}else{
cur->next=cur2;
cur=cur->next;
cur2=cur2->next;
}
}
while(cur1!=NULL){
cur->next=cur1;
cur=cur->next;
cur1=cur1->next;
}
while(cur2!=NULL){
cur->next=cur2;
cur=cur->next;
cur2=cur2->next;
}
return head->next;
}
};