Leetcode 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* p=new ListNode(0);
        ListNode* result=p;
        while(l1 && l2)
        {
            ListNode* t=new ListNode(0);
            p->next=t;
            p=p->next;
            if(l1->val<l2->val)
            {
                p->val=l1->val;
                l1=l1->next;
            }
            else
            {
                p->val=l2->val;
                l2=l2->next;
            }
            
        }
        p->next=l1?l1:l2;
        return result->next;
    }
};