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Given a linked list, reverse the nodes of a linked list k at a time and return its modified list.
k is a positive integer and is less than or equal to the length of the linked list. If the number of nodes is not a multiple of k then left-out nodes in the end should remain as it is.
Example:
Given this linked list: 1->2->3->4->5
For k = 2, you should return: 2->1->4->3->5
For k = 3, you should return: 3->2->1->4->5
Note:
Only constant extra memory is allowed.
You may not alter the values in the list's nodes, only nodes itself may be changed.
My code:
# Definition for singly-linked list.
# class ListNode:
# def __init__(self, x):
# self.val = x
# self.next = None
class Solution:
def reverseKGroup(self, head, k):
"""
:type head: ListNode
:type k: int
:rtype: ListNode
"""
if head==None:
return None
count=1
result=[]
tmp_record=[]
while head.next!=None:
if count%k==0 and count!=0:
result.append(head.val)
for i in range(k-1):
result.append(tmp_record[k-i-2])
tmp_record=[]
else:
tmp_record.append(head.val)
head=head.next
count+=1
if count%k==0:
result.append(head.val)
for i in range(k-1):
result.append(tmp_record[k-i-2])
else:
for i in range(len(tmp_record)):
result.append(tmp_record[i])
result.append(head.val)
return result
Solution:
https://leetcode.com/problems/reverse-nodes-in-k-group/