leetcode-Merge Two Sorted Lists

Question：
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.

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Solution：

/** * 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) {        if(l1 == NULL){            return l2;        }        if(l2 == NULL){            return l1;        }        ListNode* head,*cur;        if(l1->val >l2->val){            head = l2;            l2 = l2->next;        }        else{            head = l1;            l1 = l1->next;        }        cur = head;        while(l1 != NULL && l2 != NULL){            if(l1->val > l2->val){                cur->next = l2;                cur = l2;                l2 = l2->next;            }            else{                cur->next = l1;                cur = l1;                l1 = l1->next;            }        }        if(l1 == NULL){            cur->next = l2;        }        else{            cur->next = l1;        }        return head;    }};

总结：
刚开始做的时候，还在考虑要不要判断两个链表升降序的
问题，就先用升序测试了一下，结果ac.