AtCoder Grand Contest 044
E
Random Pawn
AtCoder
⌀ 3599
原题
← DF →
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Problem Statement

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You are playing a game and your goal is to maximize your expected gain. At the beginning of the game, a pawn is put, uniformly at random, at a position $p\in\{1,2,\dots, N\}$. The $N$ positions are arranged on a circle (so that $1$ is between $N$ and $2$).

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The game consists of turns. At each turn you can either end the game, and get $A_p$ dollars (where $p$ is the current position of the pawn), or pay $B_p$ dollar to keep playing. If you decide to keep playing, the pawn is randomly moved to one of the two adjacent positions $p-1$, $p+1$ (with the identifications $0 = N$ and $N+1=1$).

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What is the expected gain of an optimal strategy?

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Note: The "expected gain of an optimal strategy" shall be defined as the supremum of the expected gain among all strategies such that the game ends in a finite number of turns.

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Constraints

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  • $2 \le N \le 200,000$
  • $0 \le A_p \le 10^{12}$ for any $p = 1,\ldots, N$
  • $0 \le B_p \le 100$ for any $p = 1, \ldots, N$
  • All values in input are integers.
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Input

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Input is given from Standard Input in the following format:

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N
A_1 A_2 \cdots A_N
B_1 B_2 \cdots B_N

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Output

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Print a single real number, the expected gain of an optimal strategy. Your answer will be considered correct if its relative or absolute error does not exceed $10^{-10}$.

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样例

Input #1
5
4 2 6 3 5
1 1 1 1 1
Output #1
4.700000000000
Input #2
4
100 0 100 0
0 100 0 100
Output #2
50.000000000000
Input #3
14
4839 5400 6231 5800 6001 5200 6350 7133 7986 8012 7537 7013 6477 5912
34 54 61 32 52 61 21 43 65 12 45 21 1 4
Output #3
7047.142857142857
Input #4
10
470606482521 533212137322 116718867454 746976621474 457112271419 815899162072 641324977314 88281100571 9231169966 455007126951
26 83 30 59 100 88 84 91 54 61
Output #4
815899161079.400024414062
题目信息
题号
agc044_e
时间限制
2 s
内存限制
1024 MB

题面与样例版权归 AtCoder 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。