LeetCode21. Merge Two Sorted Lists

题目：

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.

Example:

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

题目分析：排序合并链表。用递归去实现。

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 == NULL) return l2;if (l2 == NULL) return l1;if (l1->val > l2->val) {ListNode* temp = l2;temp->next = mergeTwoLists(l1, l2->next);return temp;}else {ListNode* temp = l1;temp->next = mergeTwoLists(l1->next, l2);return temp;}}};