题目：https://leetcode-cn.com/problems/merge-two-sorted-lists/submissions/
将两个升序链表合并为一个新的 升序 链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。

我的方法：直接遍历

比较简单，直接看代码

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode() : val(0), next(nullptr) {}
 *     ListNode(int x) : val(x), next(nullptr) {}
 *     ListNode(int x, ListNode *next) : val(x), next(next) {}
 * };
 */
class Solution {
public:
    ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
        ListNode dummy;
        ListNode* tail = &dummy;

        ListNode* cur1 = l1;
        ListNode* cur2 = l2;

        while(cur1 && cur2) {
            if(cur1->val <= cur2->val) {
                tail->next = cur1;
                cur1 = cur1->next;
            }else{
                tail->next = cur2;
                cur2 = cur2->next;
            }

            tail = tail->next;
            tail->next = nullptr;
        }

        if(cur1) {
            tail->next = cur1;
        }
        if(cur2) {
            tail->next = cur2;
        }

        return dummy.next;
    }
};