21.Merge Two Sorted Lists（合并两个已排序的数组）

翻译

合并两个排好序的链表，并返回这个新链表。
新链表应该由这两个链表的头部拼接而成。

原文

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.

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(l2 == NULL) {
            return l1;
        }
        if(l1 == NULL) {
            return l2;
        }
        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;
        }
    }
};