21. 合并两个有序链表 

 1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     struct ListNode *next;
 6  * };
 7  */
 8 
 9 
10 struct ListNode* mergeTwoLists(struct ListNode* l1, struct ListNode* l2){
11     struct ListNode *head=(struct ListNode *)malloc(sizeof(struct ListNode)) ,*tail;
12     head->next = NULL;
13     tail = head;
14 
15     while(l1 && l2)
16     {
17         if(l1->val<=l2->val){
18             struct ListNode * p = (struct ListNode *)malloc(sizeof(struct ListNode));
19             p->next = NULL;
20             p->val = l1->val;
21             tail->next = p;
22             tail =p;
23             l1 = l1->next;
24         }else{
25             struct ListNode * p = (struct ListNode *)malloc(sizeof(struct ListNode));
26             p->next = NULL;
27             p->val = l2->val;
28             tail->next = p;
29             tail =p;
30             l2 = l2->next;
31         }
32     }
33     if(l1)    //如果去掉这2个if如果l1之后还有节点,l2之后无节点，根据执行顺序就会使整个链表无节点，这2个if的作用是,把剩余节点的链表链接在尾部
34     tail->next = l1;
35     if(l2)  //  
36     tail->next = l2;
37     return head->next;
38 }

 

posted @ 2021-06-15 16:25  传说中的旅行者  阅读(39)  评论(0)    收藏  举报