21 Merge Two Sorted Lists(两链表归并排序Easy)

 1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     ListNode *next;
 6  *     ListNode(int x) : val(x), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11     ListNode* mergeTwoLists(ListNode* l1, ListNode* l2) {
12         ListNode* head=new ListNode(0);
13         ListNode* p=head;
14         while(l1&&l2){
15             if(l1->val<=l2->val){
16                 p->next=l1;
17                 l1=l1->next;
18                 p=p->next;
19             }
20             else{
21                 p->next=l2;
22                 l2=l2->next;
23                 p=p->next;
24             }
25         }
26         if(l1)p->next=l1;
27         if(l2)p->next=l2;
28         return head->next;    //第一个节点去掉
29     }
30 };