Codeforces Round 846 (Div. 2)
B
GCD Partition
Codeforces
1100
原题
← AD →
翻译中…

While at Kira's house, Josuke saw a piece of paper on the table with a task written on it.

翻译中…

The task sounded as follows. There is an array $a$ of length $n$. On this array, do the following:

翻译中…
  • select an integer $k \gt 1$;
  • split the array into $k$ subsegments $^\dagger$;
  • calculate the sum in each of $k$ subsegments and write these sums to another array $b$ (where the sum of the subsegment $(l, r)$ is ${\sum_{j = l}^{r}a_j}$);
  • the final score of such a split will be $\gcd(b_1, b_2, \ldots, b_k)^\ddagger$.
翻译中…

The task is to find such a partition that the score is maximum possible. Josuke is interested in this task but is not strong in computer science. Help him to find the maximum possible score.

翻译中…

$^\dagger$ A division of an array into $k$ subsegments is $k$ pairs of numbers $(l_1, r_1), (l_2, r_2), \ldots, (l_k, r_k)$ such that $l_i \le r_i$ and for every $1 \le j \le k - 1$ $l_{j + 1} = r_j + 1$, also $l_1 = 1$ and $r_k = n$. These pairs represent the subsegments.

翻译中…

$^\ddagger$ $\gcd(b_1, b_2, \ldots, b_k)$ stands for the greatest common divisor (GCD) of the array $b$.

翻译中…

Input

翻译中…

The first line contains a single number $t$ ($1 \le t \le 10^4$) — the number of test cases.

翻译中…

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

翻译中…

The second line contains $n$ integers $a_1, a_2, a_3, \ldots, a_n$ ($1 \le a_i \le 10^9 $) — the array $a$ itself.

翻译中…

It is guaranteed that the sum of $n$ over all test cases does not exceed $2 \cdot 10^5$.

翻译中…

Output

翻译中…

For each test case print a single integer — the maximum score for the optimal partition.

翻译中…

Note

翻译中…

In the first test case, you can choose $k = 2$ and split the array into subsegments $(1, 2)$ and $(3, 4)$.

翻译中…

Then the score of such a partition will be equal to $\gcd(a_1 + a_2, a_3 + a_4) = \gcd(2 + 2, 1 + 3) = \gcd(4, 4) = 4$.

翻译中…

In the fourth test case, you can choose $k = 3$ and split the array into subsegments $(1, 2), (3, 5), (6, 6)$.

翻译中…

The split score is $\gcd(1 + 2, 1 + 1 + 1, 3) = 3$.

翻译中…

样例

Input #1
6
4
2 2 1 3
2
1 2
3
1 4 5
6
1 2 1 1 1 3
10
12 30 37 88 12 78 89 17 2 12
6
7 7 7 7 7 7
Output #1
4
1
5
3
1
21
InputCopy OutputCopy
题目信息
题号
1780B
时间限制
1 s
内存限制
256 MB
标签
暴力
贪心
数学
数论

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。