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4624：Endless Spin
题目描述
I spin it again and again,and throw it away finally.
So now I have a row of n ball,named from 1 to n,each ball is white initially.
At each step I randomly chose a interval [l, r] and paint all ball in this interval to black.
It means every
interval have a equal chance of being chosen.
And I'll stop if all ball are black.What is the expected steps before I stop?
So now I have a row of n ball,named from 1 to n,each ball is white initially.
At each step I randomly chose a interval [l, r] and paint all ball in this interval to black.
It means every
interval have a equal chance of being chosen.And I'll stop if all ball are black.What is the expected steps before I stop?
输入解释
The first line contains integer T(1<=T<=50). Denoting the number of the test cases.
Then T lines follows, each line contains an integer n (1<=n<=50).
Then T lines follows, each line contains an integer n (1<=n<=50).
输出解释
For each test cases,print the answer in a line.
Print the answer rounded to 15 decimal places.
Print the answer rounded to 15 decimal places.
输入样例
3 1 2 3
输出样例
1.000000000000000 2.000000000000000 2.900000000000000
提示
不建议使用long double
来自杭电HDUOJ的附加信息
| Author | WJMZBMR |
| Recommend | zhuyuanchen520 |
最后修改于 2020-10-25T23:15:13+00:00 由爬虫自动更新
共提交 0 次
通过率 --%
| 时间上限 | 内存上限 |
| 4000/2000MS(Java/Others) | 32768/32768K(Java/Others) |
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