[leetcode]Rotate List @ Python

原题地址:https://oj.leetcode.com/problems/rotate-list/

题意:

Given a list, rotate the list to the right by k places, where k is non-negative.

For example:
Given 1->2->3->4->5->NULL and k = 2,
return 4->5->1->2->3->NULL.

解题思路:循环右移一条链表,比如k=2,(1,2,3,4,5)循环右移两位变为(4,5,1,2,3)。由于k值有可能比链表长度大很多,所以先要用一个count变量求出链表的长度。而k%count就是循环右移的步数。

代码:

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

class Solution:
    # @param head, a ListNode
    # @param k, an integer
    # @return a ListNode
    def rotateRight(self, head, k):
        if k == 0:
            return head
        if head == None:
            return head
        dummy = ListNode(0)
        dummy.next = head
        p = dummy
        count = 0
        while p.next:
            p = p.next
            count += 1
        p.next = dummy.next
        step = count - ( k % count )
        for i in range(0, step):
            p = p.next
        head = p.next
        p.next = None
        return head
        

 

posted @ 2014-06-13 11:19  南郭子綦  阅读(3598)  评论(0编辑  收藏  举报