21 Merge Two Sorted Lists

/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
ListNode* head = new ListNode(0);
ListNode* now = head;
while(l1&&l2)
{
if(l1->val<l2->val)
{
now->next = l1;
l1 = l1->next;
}
else
{
now->next = l2;
l2 = l2->next;
}
now = now->next;
}
if(l1==NULL)
now->next = l2;
else
now->next = l1;
return head->next;
}
};