CF1557A.Ezzat and Two Subsequences

传统题 时间 2000 ms 内存 256 MiB 3 尝试 1 已通过 1 标签

Ezzat and Two Subsequences

Ezzat has an array of nn integers (maybe negative). He wants to split it into two non-empty subsequences aa and bb, such that every element from the array belongs to exactly one subsequence, and the value of f(a)+f(b)f(a) + f(b) is the maximum possible value, where f(x)f(x) is the average of the subsequence xx.

A sequence xx is a subsequence of a sequence yy if xx can be obtained from yy by deletion of several (possibly, zero or all) elements.

The average of a subsequence is the sum of the numbers of this subsequence divided by the size of the subsequence.

For example, the average of [1,5,6][1,5,6] is (1+5+6)/3=12/3=4(1+5+6)/3 = 12/3 = 4, so f([1,5,6])=4f([1,5,6]) = 4.

Input

The first line contains a single integer tt (1t1031 \le t \le 10^3)— the number of test cases. Each test case consists of two lines.

The first line contains a single integer nn (2n1052 \le n \le 10^5).

The second line contains nn integers a1,a2,,ana_1, a_2, \ldots, a_n (109ai109-10^9 \le a_i \le 10^9).

It is guaranteed that the sum of nn over all test cases does not exceed 31053\cdot10^5.

Output

For each test case, print a single value — the maximum value that Ezzat can achieve.

Your answer is considered correct if its absolute or relative error does not exceed 10610^{-6}.

Formally, let your answer be aa, and the jury's answer be bb. Your answer is accepted if and only if abmax(1,b)106\frac{|a - b|}{\max{(1, |b|)}} \le 10^{-6}.

Note

In the first test case, the array is [3,1,2][3, 1, 2]. These are all the possible ways to split this array:

  • a=[3]a = [3], b=[1,2]b = [1,2], so the value of f(a)+f(b)=3+1.5=4.5f(a) + f(b) = 3 + 1.5 = 4.5.
  • a=[3,1]a = [3,1], b=[2]b = [2], so the value of f(a)+f(b)=2+2=4f(a) + f(b) = 2 + 2 = 4.
  • a=[3,2]a = [3,2], b=[1]b = [1], so the value of f(a)+f(b)=2.5+1=3.5f(a) + f(b) = 2.5 + 1 = 3.5.

Therefore, the maximum possible value 4.54.5.

In the second test case, the array is [7,6,6][-7, -6, -6]. These are all the possible ways to split this array:

  • a=[7]a = [-7], b=[6,6]b = [-6,-6], so the value of f(a)+f(b)=(7)+(6)=13f(a) + f(b) = (-7) + (-6) = -13.
  • a=[7,6]a = [-7,-6], b=[6]b = [-6], so the value of f(a)+f(b)=(6.5)+(6)=12.5f(a) + f(b) = (-6.5) + (-6) = -12.5.

Therefore, the maximum possible value 12.5-12.5.

Samples

4
3
3 1 2
3
-7 -6 -6
3
2 2 2
4
17 3 5 -3
4.500000000
-12.500000000
4.000000000
18.666666667

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