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.

代碼如下：

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;
        
    }
};