[容易]翻转链表

 1 class Solution {
 2 public:
 3     /**
 4      * @param head: The first node of linked list.
 5      * @return: The new head of reversed linked list.
 6      */
 7     ListNode *reverse(ListNode *head) {
 8         // write your code here
 9         ListNode *temp1=NULL;
10         ListNode *temp2=head;
11         while(head!=NULL)
12             {
13                 head=head->next;
14                 temp2->next=temp1;
15                 temp1=temp2;        
16                 temp2=head;
17             }
18         return temp1;
19     }
20 };

 1 /**
 2  * Definition of ListNode
 3  * 
 4  * class ListNode {
 5  * public:
 6  *     int val;
 7  *     ListNode *next;
 8  * 
 9  *     ListNode(int val) {
10  *         this->val = val;
11  *         this->next = NULL;
12  *     }
13  * }
14  */
15 class Solution {
16 public:
17     /**
18      * @param head: The first node of linked list.
19      * @return: The new head of reversed linked list.
20      */
21     ListNode *reverse(ListNode *head) {
22         ListNode *prev = NULL;
23         while (head != NULL) {
24             ListNode *temp = head->next;
25             head->next = prev;
26             prev = head;
27             head = temp;
28         }
29         return prev;
30     }
31 };

 1 #include <iostream>
 2 using namespace std;
 3 
 4 class ListNode {
 5 public:
 6     int val;
 7     ListNode *next;
 8     ListNode(int val) {
 9         this->val = val;
10         this->next = NULL;
11     }
12 };
13 
14 class Solution {
15 public:
16     /**
17      * @param head: The first node of linked list.
18      * @return: The new head of reversed linked list.
19      */
20     ListNode *reverse(ListNode *head) {
21         // write your code here
22         ListNode *temp1=NULL;
23         ListNode *temp2=head;
24         while(head!=NULL)
25             {
26                 head=head->next;
27                 temp2->next=temp1;
28                 temp1=temp2;        
29                 temp2=head;
30             }
31         return temp1;
32     }
33 };
34 
35 int main()
36 {
37     Solution solu;
38     //动态创建链表
39     ListNode *head,*temp,*result;
40     head=new ListNode(10);
41     temp=head;
42     temp->next=new ListNode(20);
43     temp=temp->next;
44     temp->next=new ListNode(30);
45     temp=temp->next;
46     temp->next=NULL;
47     //输出翻转后的结果
48     result=solu.reverse(head);
49     temp=result;
50     cout<<temp->val<<" "<<temp->next->val<<" "<<temp->next->next->val<<endl;
51 }