反转链表

c++

栈方法

 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* ReverseList(ListNode* pHead) {
12         if(!pHead || !pHead->next) return pHead;
13         stack<ListNode*> res;
14         ListNode* p = pHead;
15         ListNode* newhead;
16         while(p->next){
17             res.push(p);
18             p = p->next;
19         }
20         //此时p是最后一个结点
21         newhead = p;
22         while(!res.empty()){
23             p->next = res.top();
24             p = p->next;
25             res.pop();
26         }
27         //此时p到了反转之后的最后一个结点
28         p->next = NULL;
29         return newhead;
30     }
31 };

python

指针法

 1 # -*- coding:utf-8 -*-
 2 # class ListNode:
 3 #     def __init__(self, x):
 4 #         self.val = x
 5 #         self.next = None
 6 class Solution:
 7     # 返回ListNode
 8     def ReverseList(self, pHead):
 9         # write code here
10         if pHead==None or pHead.next==None:
11             return pHead
12         last = None
13         cur = pHead
14         while cur!=None:
15             temp = cur.next
16             cur.next = last
17             last = cur
18             cur = temp
19         return last

 

posted @ 2019-07-04 16:16  Austin_anheqiao  阅读(124)  评论(0)  编辑  收藏  举报