leetcode——25. K 个一组翻转链表

用栈做：

# Definition for singly-linked list.
# class ListNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution(object):
    def reverseKGroup(self, head, k):
        """
        :type head: ListNode
        :type k: int
        :rtype: ListNode
        """
        dummy=ListNode(0)
        p=dummy
        while True:
            count=k
            stack=[]
            tmp=head
            while count and tmp:
                stack.append(tmp)
                tmp=tmp.next
                count-=1
            if count:
                p.next=head
                break
            while stack:
                p.next=stack.pop()
                p=p.next
            p.next=tmp
            head=tmp
        return dummy.next

执行用时 :32 ms, 在所有 python 提交中击败了95.97%的用户

内存消耗 :13.2 MB, 在所有 python 提交中击败了44.26%的用户

 

 

——2019.10.31