Codeforces Round 848 (Div. 2)
A
Flip Flop Sum
Codeforces
800
原题
←B →
翻译中…

You are given an array of $n$ integers $a_1, a_2, \ldots, a_n$. The integers are either $1$ or $-1$. You have to perform the following operation exactly once on the array $a$:

翻译中…
  • Choose an index $i$ ($1 \leq i \lt n$) and flip the signs of $a_i$ and $a_{i+1}$. Here, flipping the sign means $-1$ will be $1$ and $1$ will be $-1$.
翻译中…

What is the maximum possible value of $a_1 + a_2 + \ldots + a_n$ after applying the above operation?

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Input

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Each test contains multiple test cases. The first line contains the number of test cases $t$ ($1 \le t \le 500$). Description of the test cases follows.

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The first line of each test case contains a single integer $n$ ($2 \le n \le 10^5$), the length of the array $a$.

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The next line contains $n$ integers $a_1, a_2, \ldots, a_n$ ($a_i = 1$ or $a_i = -1$).

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The sum of $n$ over all cases doesn't exceed $10^5$.

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Output

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For each test case, print the maximum possible sum of the array $a$ you can get in a separate line.

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Note

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In the first case, we can choose index $4$ and flip the signs of $a_4$ and $a_5$. After this operation, the sum will be $-1+1+1+1+1 = 3$. We can't make the sum larger than this.

翻译中…

In the third case, the only option is to choose the index $1$.

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样例

Input #1
4
5
-1 1 1 -1 -1
5
1 1 -1 -1 -1
2
1 1
4
1 -1 -1 1
Output #1
3
3
-2
4
InputCopy OutputCopy
题目信息
题号
1778A
时间限制
1 s
内存限制
256 MB
标签
贪心
模拟

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。