[LeetCode]Reveal Cards In Increasing Order

题目描述:

LeetCode 950. Reveal Cards In Increasing Order

In a deck of cards, every card has a unique integer.  You can order the deck in any order you want.

Initially, all the cards start face down (unrevealed) in one deck.

Now, you do the following steps repeatedly, until all cards are revealed:

  1. Take the top card of the deck, reveal it, and take it out of the deck.
  2. If there are still cards in the deck, put the next top card of the deck at the bottom of the deck.
  3. If there are still unrevealed cards, go back to step 1.  Otherwise, stop.

Return an ordering of the deck that would reveal the cards in increasing order.

The first entry in the answer is considered to be the top of the deck.

Example 1:

Input: [17,13,11,2,3,5,7]
Output: [2,13,3,11,5,17,7]
Explanation: 
We get the deck in the order [17,13,11,2,3,5,7] (this order doesn't matter), and reorder it.
After reordering, the deck starts as [2,13,3,11,5,17,7], where 2 is the top of the deck.
We reveal 2, and move 13 to the bottom.  The deck is now [3,11,5,17,7,13].
We reveal 3, and move 11 to the bottom.  The deck is now [5,17,7,13,11].
We reveal 5, and move 17 to the bottom.  The deck is now [7,13,11,17].
We reveal 7, and move 13 to the bottom.  The deck is now [11,17,13].
We reveal 11, and move 17 to the bottom.  The deck is now [13,17].
We reveal 13, and move 17 to the bottom.  The deck is now [17].
We reveal 17.
Since all the cards revealed are in increasing order, the answer is correct.

Note:

  1. 1 <= A.length <= 1000
  2. 1 <= A[i] <= 10^6
  3. A[i] != A[j] for all i != j

题目大意:

给定一副扑克,每张牌有一个唯一整数。你可以按照任意顺序对扑克重新排序。

开始时,所有牌背面朝上。

重复如下操作,直到所有牌都正面朝上。

1. 从牌堆顶那一张牌,翻面移走
2. 如果牌堆还有扑克,将一张牌移动至牌堆底部
3. 重复操作1直到所有牌均翻面

返回可以使得翻牌序号递增有序的牌堆顺序。

解题思路:

队列(Queue) + 模拟(Simulation)

初始化队列queue为递增序号[0, 1, 2, ..., len(deck) - 1]

将输入的扑克deck从小到大排序

利用映射cmap维护序号与扑克之间的映射关系

用queue模拟翻牌过程,记队列头部元素为t,计数器cnt记录当前的执行次数

cnt为奇数时,令cmap[t] = deck.pop(0)

cnt为偶数时,将t加入queue的尾部

重复执行如上过程,直到queue为空。

将cmap按照key排序,输出value即为答案。

Python代码:

class Solution(object):
    def deckRevealedIncreasing(self, deck):
        """
        :type deck: List[int]
        :rtype: List[int]
        """
        deck.sort()
        size = len(deck)
        queue = list(range(size))
        cnt = 0
        cmap = [None] * size
        while queue:
            cnt += 1
            t = queue.pop(0)
            if cnt % 2:
                cmap[t] = deck.pop(0)
            else:
                queue.append(t)
        return [cmap[x] for x in range(size)]

 

本文链接:http://bookshadow.com/weblog/2018/12/02/leetcode-reveal-cards-in-increasing-order/
请尊重作者的劳动成果,转载请注明出处!书影博客保留对文章的所有权利。

如果您喜欢这篇博文,欢迎您捐赠书影博客: ,查看支付宝二维码

Pingbacks已关闭。

暂无评论

张贴您的评论