翻转一个链表
样例：给出一个链表1->2->3->null，这个翻转后的链表为3->2->1->null
一种比较简单的方法是用“摘除法”。就是先新建一个空节点，然后遍历整个链表，依次令遍历到的节点指向新建链表的头节点。
那样例来说，步骤是这样的：
1. 新建空节点：None
2. 1->None
3. 2->1->None
4. 3->2->1->None
代码就非常简单了：
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
|
""" Definition of ListNode class ListNode(object): def __init__(self, val, next=None): self.val = val self.next = next """class Solution: """ @param head: The first node of the linked list. @return: You should return the head of the reversed linked list. Reverse it in-place. """ def reverse(self, head): temp = None while head: cur = head.next head.next = temp temp = head head = cur return temp # write your code here |
当然，还有一种稍微难度大一点的解法。我们可以对链表中节点依次摘链和链接的方法写出原地翻转的代码：
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
|
""" Definition of ListNode class ListNode(object): def __init__(self, val, next=None): self.val = val self.next = next """class Solution: """ @param head: The first node of the linked list. @return: You should return the head of the reversed linked list. Reverse it in-place. """ def reverse(self, head): if head is None: return head dummy = ListNode(-1) dummy.next = head pre, cur = head, head.next while cur: temp = cur # 把摘链的地方连起来 pre.next = cur.next cur = pre.next temp.next = dummy.next dummy.next = temp return dummy.next # write your code here |
需要注意的是，做摘链的时候，不要忘了把摘除的地方再连起来
感谢阅读，希望能帮助到大家，谢谢大家对本站的支持！
