面试题17 合并两个排序的链表

题目描述

输入两个单调递增的链表，输出两个链表合成后的链表，当然我们需要合成后的链表满足单调不减规则。

 1 /*
 2 struct ListNode {
 3     int val;
 4     struct ListNode *next;
 5     ListNode(int x) :
 6             val(x), next(NULL) {
 7     }
 8 };*/
 9 class Solution {
10 public:
11     ListNode* Merge(ListNode* pHead1, ListNode* pHead2)
12     {
13         if (pHead1 == NULL){
14             return pHead2;
15         }
16         if (pHead2 == NULL){
17             return pHead1;
18         }
19         ListNode *p = NULL;
20         if (pHead1->val < pHead2->val){
21             p = pHead1;
22             p->next = Merge(pHead1->next, pHead2);
23         }
24         else{
25             p = pHead2;
26             p->next = Merge(pHead1, pHead2->next);
27         }
28         return p;
29     }
30 };