Codeforces Round 730 (Div. 2)
C
Need for Pink Slips
Codeforces
1900
原题
← BD1 →
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After defeating a Blacklist Rival, you get a chance to draw $1$ reward slip out of $x$ hidden valid slips. Initially, $x=3$ and these hidden valid slips are Cash Slip, Impound Strike Release Marker and Pink Slip of Rival's Car. Initially, the probability of drawing these in a random guess are $c$, $m$, and $p$, respectively. There is also a volatility factor $v$. You can play any number of Rival Races as long as you don't draw a Pink Slip. Assume that you win each race and get a chance to draw a reward slip. In each draw, you draw one of the $x$ valid items with their respective probabilities. Suppose you draw a particular item and its probability of drawing before the draw was $a$. Then,

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  • If the item was a Pink Slip, the quest is over, and you will not play any more races.
  • Otherwise,
  • If $a\leq v$, the probability of the item drawn becomes $0$ and the item is no longer a valid item for all the further draws, reducing $x$ by $1$. Moreover, the reduced probability $a$ is distributed equally among the other remaining valid items.
    • If $a \gt v$, the probability of the item drawn reduces by $v$ and the reduced probability is distributed equally among the other valid items.
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For example,

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  • If $(c,m,p)=(0.2,0.1,0.7)$ and $v=0.1$, after drawing Cash, the new probabilities will be $(0.1,0.15,0.75)$.
  • If $(c,m,p)=(0.1,0.2,0.7)$ and $v=0.2$, after drawing Cash, the new probabilities will be $(Invalid,0.25,0.75)$.
  • If $(c,m,p)=(0.2,Invalid,0.8)$ and $v=0.1$, after drawing Cash, the new probabilities will be $(0.1,Invalid,0.9)$.
  • If $(c,m,p)=(0.1,Invalid,0.9)$ and $v=0.2$, after drawing Cash, the new probabilities will be $(Invalid,Invalid,1.0)$.
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You need the cars of Rivals. So, you need to find the expected number of races that you must play in order to draw a pink slip.

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Input

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The first line of input contains a single integer $t$ ($1\leq t\leq 10$)  — the number of test cases.

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The first and the only line of each test case contains four real numbers $c$, $m$, $p$ and $v$ ($0 \lt c,m,p \lt 1$, $c+m+p=1$, $0.1\leq v\leq 0.9$).

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Additionally, it is guaranteed that each of $c$, $m$, $p$ and $v$ have at most $4$ decimal places.

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Output

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For each test case, output a single line containing a single real number — the expected number of races that you must play in order to draw a Pink Slip.

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Your answer is considered correct if its absolute or relative error does not exceed $10^{-6}$.

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Formally, let your answer be $a$, and the jury's answer be $b$. Your answer is accepted if and only if $\frac{|a - b|}{\max{(1, |b|)}} \le 10^{-6}$.

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Note

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For the first test case, the possible drawing sequences are:

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  • P with a probability of $0.6$;
  • CP with a probability of $0.2\cdot 0.7 = 0.14$;
  • CMP with a probability of $0.2\cdot 0.3\cdot 0.9 = 0.054$;
  • CMMP with a probability of $0.2\cdot 0.3\cdot 0.1\cdot 1 = 0.006$;
  • MP with a probability of $0.2\cdot 0.7 = 0.14$;
  • MCP with a probability of $0.2\cdot 0.3\cdot 0.9 = 0.054$;
  • MCCP with a probability of $0.2\cdot 0.3\cdot 0.1\cdot 1 = 0.006$.
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So, the expected number of races is equal to $1\cdot 0.6 + 2\cdot 0.14 + 3\cdot 0.054 + 4\cdot 0.006 + 2\cdot 0.14 + 3\cdot 0.054 + 4\cdot 0.006 = 1.532$.

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For the second test case, the possible drawing sequences are:

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  • P with a probability of $0.4$;
  • CP with a probability of $0.4\cdot 0.6 = 0.24$;
  • CMP with a probability of $0.4\cdot 0.4\cdot 1 = 0.16$;
  • MP with a probability of $0.2\cdot 0.5 = 0.1$;
  • MCP with a probability of $0.2\cdot 0.5\cdot 1 = 0.1$.
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So, the expected number of races is equal to $1\cdot 0.4 + 2\cdot 0.24 + 3\cdot 0.16 + 2\cdot 0.1 + 3\cdot 0.1 = 1.86$.

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样例

Input #1
4
0.2 0.2 0.6 0.2
0.4 0.2 0.4 0.8
0.4998 0.4998 0.0004 0.1666
0.3125 0.6561 0.0314 0.2048
Output #1
1.532000000000
1.860000000000
5.005050776521
4.260163673896
InputCopy OutputCopy
题目信息
题号
1543C
时间限制
1 s
内存限制
256 MB
标签
位运算
暴力
DFS 及类似
模拟
数学
概率论

题面与样例版权归 Codeforces 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。