puzzleup 2018

nayi224 · 发表于 2018-9-7 14:19

newkid 发表于 2018-9-6 21:43
再帮你化简一下：
with t as (select chr(64 + level) n from dual connect by level

玉兔我要开满鲜花~

newkid · 发表于 2018-9-7 22:06

玉兔已转让，秀才转不了，我特地给丸喵喵发PM让她颁发给你。

newkid · 发表于 2018-9-7 22:08

lugionline 发表于 2018-9-7 09:30
绝对的暴力，和MMA比简洁，哼

简洁有啥用，反人类的语言。

solomon_007 · 发表于 2018-9-8 20:29

newkid 发表于 2018-9-7 22:06
玉兔已转让，秀才转不了，我特地给丸喵喵发PM让她颁发给你。

发不了，你随便转个能转的也可以

newkid · 发表于 2018-9-12 23:16

#7 DICE GAME

You will play a game with a fair 6-sided die. You will throw the die and as long as the result of the throw is greater than or equal to the previous throw, you will continue throwing. If the throw is lower than the previous one, you will stop and get as many points as the sum of all throws, including the last one. For example, if you get 2, 5, 5, and 3 as a result of 4 throws, the game will end with 15 points.

What is the expected value of the points you will get at the end of the game?

Enter your answer as a reduced fraction. Example: 123/4567

你用一个6面均匀的骰子玩一个游戏。你掷出骰子，只要结果大于或等于前一次投掷，你就继续投掷。如果投掷结果小于前一次就将停止，得到的总分等于所有投掷结果的总和，包括最后一次。例如，假设你4次投掷的结果是2,5,5和3，则游戏将以15分结束。

在游戏结束时你的得分预期值是多少？

用简化分数输入你的答案，例如：123/4567

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这个应该有期望值公式可以套用。

newkid · 发表于 2018-9-12 23:16

solomon_007 发表于 2018-9-8 20:29
发不了，你随便转个能转的也可以

喵喵说已经给你发了秀才。

solomon_007 · 发表于 2018-9-13 15:29

7#

我只能算这个期望的大概值，不好写出最简整数比

with t as (select level n from dual connect by level <=6),
   s(lvl,nlist,n_sum,last_n) as (select 1,cast(n as varchar2(100)),n,n from t
                           union all
                           select s.lvl + 1,
                                 s.nlist||t.n,
                                 s.n_sum + t.n,
                                 t.n
                           from s,t
                           where t.n >= s.last_n
                              and s.lvl < 20 - 1)
select sum(p_val)
  from (
select --s.lvl + 1,
   sum(s.n_sum+t.n)*power(6,-1*(s.lvl+1)) p_val
  from s, t
where s.last_n > t.n
group by s.lvl + 1)

14 : 10.4509360622632
15 : 10.4509421212827
16 : 10.4509435639064
17 : 10.4509439005186
18 : 10.4509439776589
19 : 10.4509439950533
20 : 10.4509439989187

这期望值大约 10.4509，最长步长分别14，15，。。。，20