编程介的小学生 2017-09-04 23:45 采纳率: 20.5%
浏览 727
已采纳

Dumb Bones

You are trying to set up a straight line of dominos, standing on end, to be pushed over later for your entertainment. (Sure, it seems pointless to set something up only to knock it down again, but you have some strange hobbies) The tricky thing about setting dominos, however, is that if you make a mistake and knock one over as you place it, it will knock down any adjacent line of consecutive dominos on one side of it, partially ruining your work.

For instance, if you've already placed dominos in the pattern DD__DxDDD_D, and you try placing a domino at position x, there is a chance it will fall and knock over the domino to the left or the three dominos to its right, forcing you to place them again.
This human error is somewhat unavoidable, but you can make the odds somewhat more favourable by using a domino-placing technique that leads to dominos falling in one direction more often than in the other.

Given the number of dominos you are trying to set up, and the probability that you'll knock over any individual domino either to the left or to the right while placing it, determine the average number of dominos you'll need to place before you finish. Assume that you're using an optimal placement strategy.

Input

Input will consist of up to 100 cases. Each case consists of one line of input. It will contain the number of dominos to place, n, 1 <= n <= 1000, followed by nonnegative values Pl and Pr, indicating the probability of any domino falling to the left or to the right when placed. You may assume 0 < Pl + Pr <= 0.5.

The last test case is followed by a line containing a single 0.

Output

For each case, output the expected number of dominos that will need to be placed before you finish, accurate to two digits after the decimal.

Sample Input

10 0.25 0.25
10 0.1 0.4
10 0.0 0.5
0

Sample Output

46.25
37.28
20.00

  • 写回答

2条回答 默认 最新

  • threenewbee 2017-09-07 15:47
    关注
    本回答被题主选为最佳回答 , 对您是否有帮助呢?
    评论
查看更多回答(1条)

报告相同问题?

悬赏问题

  • ¥30 帮我写一段可以读取LD2450数据并计算距离的Arduino代码
  • ¥15 C#调用python代码(python带有库)
  • ¥15 矩阵加法的规则是两个矩阵中对应位置的数的绝对值进行加和
  • ¥15 活动选择题。最多可以参加几个项目?
  • ¥15 飞机曲面部件如机翼,壁板等具体的孔位模型
  • ¥15 vs2019中数据导出问题
  • ¥20 云服务Linux系统TCP-MSS值修改?
  • ¥20 关于#单片机#的问题:项目:使用模拟iic与ov2640通讯环境:F407问题:读取的ID号总是0xff,自己调了调发现在读从机数据时,SDA线上并未有信号变化(语言-c语言)
  • ¥20 怎么在stm32门禁成品上增加查询记录功能
  • ¥15 Source insight编写代码后使用CCS5.2版本import之后,代码跳到注释行里面