链表反转

 1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     struct ListNode *next;
 6  * };
 7  */
 8 struct ListNode* reverseList(struct ListNode* head){
 9     if (head == NULL || head->next == NULL)
10         return head;
11     
12     struct ListNode *pre = head;
13     struct ListNode *cur = head->next;
14     struct ListNode *tmp = head->next->next;
15     
16     while(cur)
17     {
18         tmp = cur->next;
19         cur->next = pre;
20         pre = cur;
21         cur = tmp;
22     }
23     head->next = NULL;
24     
25     return pre;
26 
27 }

 1 struct ListNode* reverseList(struct ListNode* head){
 2     if (head == NULL || head->next == NULL)
 3         return head;
 4     else
 5     {
 6         struct ListNode *newhead = reverseList(head->next);
 7         head->next->next = head;
 8         head->next = NULL;
 9         return newhead;
10         
11     }
12 }