LeetCode 21. Merge Two Sorted Lists (Easy)

题目描述：

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.

题目大意：合并两个排序好的链表，使得新链表也是排序好的。

思路：额没什么好说的，直接做，递归。

c++代码：

/** * 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 == nullptr)            return l2;        if (l2 == nullptr)            return l1;        if (l1->val <= l2->val)        {            l1->next = mergeTwoLists(l1->next, l2);            return l1;        }        else        {            l2->next = mergeTwoLists(l1, l2->next);            return l2;        }    }};