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.

代码如下：

class Solution {public:    ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {        if(l1 == NULL)            return l2;        if(l2 == NULL)            return l1;                ListNode *dummy = new ListNode(0);        ListNode *MergedList = dummy;                    while(l1 && l2){            if(l1->val < l2->val){                dummy->next = l1;                l1 = l1->next;            }else{                dummy->next = l2;                l2 = l2->next;            }            dummy = dummy->next;                        }                if(l1){            dummy->next = l1;        }                if(l2){            dummy->next = l2;        }                return MergedList->next;            }};