21. Merge Two Sorted Lists

description:

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.
Note:

Example:

Example:

Input: 1->2->4, 1->3->4
Output: 1->1->2->3->4->4

my answer:

感恩

my answer

一个一个比下去

大佬的answer：

class Solution {
public:
    ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
        ListNode *dummy = new ListNode(-1), *cur = dummy;
        while(l1 && l2){
            if(l1->val < l2->val){
                cur->next = l1;
                l1 = l1->next;
            }
            else{
                cur->next = l2;
                l2 = l2->next;
            }
            cur = cur->next;
        }
        cur->next = l1 ? l1 : l2;
        return dummy->next;
    }
};

relative point get√：

链表节点的定义/指针的定义 ListNode *dummy（指针） = new ListNode(-1)（结点）

hint :