35. 翻转链表
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
挑战
在原地一次翻转完成
/**
* Definition for ListNode
* public class ListNode {
* int val;
* ListNode next;
* ListNode(int x) {
* val = x;
* next = null;
* }
* }
*/
public class Solution {
/**
* @param head: n
* @return: The new head of reversed linked list.
*/
public ListNode reverse(ListNode head) {
// write your code here
if(head==null || head.next==null) return head;
ListNode curr=null;
while(head!=null)
{
ListNode temp=head.next;
head.next=curr;
curr=head;
head=temp;
}
return curr;
}
}
####################################################################
/**
* Definition of singly-linked-list:
*
* class ListNode {
* public:
* int val;
* ListNode *next;
* ListNode(int val) {
* this->val = val;
* this->next = NULL;
* }
* }
*/
class Solution {
public:
/**
* @param head: n
* @return: The new head of reversed linked list.
*/
ListNode * reverse(ListNode * head) {
// write your code here
if(head==NULL || head->next==NULL) return head;
ListNode* res=NULL;
while(head!=NULL)
{
ListNode* tmp=head->next;
head->next=res;
res=head;
head=tmp;
}
return res;
}
};
############################################################
"""
Definition of ListNode
class ListNode(object):
def __init__(self, val, next=None):
self.val = val
self.next = next
"""
class Solution:
"""
@param head: n
@return: The new head of reversed linked list.
"""
def reverse(self, head):
# write your code here
if head==None or head.next==None:
return head
res=None
while head!=None:
tmp=head.next
head.next=res
res=head
head=tmp
return res