Codeforces Round 846 (Div. 2) |
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Finished |
While at Kira's house, Josuke saw a piece of paper on the table with a task written on it.
The task sounded as follows. There is an array $$$a$$$ of length $$$n$$$. On this array, do the following:
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.
$$$^\dagger$$$ 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.
$$$^\ddagger$$$ $$$\gcd(b_1, b_2, \ldots, b_k)$$$ stands for the greatest common divisor (GCD) of the array $$$b$$$.
The first line contains a single number $$$t$$$ ($$$1 \le t \le 10^4$$$) — the number of test cases.
For each test case, the first line contains one integer $$$n$$$ ($$$2 \le n \le 2 \cdot 10^5$$$) — the length of the array $$$a$$$.
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.
It is guaranteed that the sum of $$$n$$$ over all test cases does not exceed $$$2 \cdot 10^5$$$.
For each test case print a single integer — the maximum score for the optimal partition.
642 2 1 321 231 4 561 2 1 1 1 31012 30 37 88 12 78 89 17 2 1267 7 7 7 7 7
4 1 5 3 1 21
In the first test case, you can choose $$$k = 2$$$ and split the array into subsegments $$$(1, 2)$$$ and $$$(3, 4)$$$.
Then the score of such a partition will be equal to $$$\gcd(a_1 + a_2, a_3 + a_4) = \gcd(2 + 2, 1 + 3) = \gcd(4, 4) = 4$$$.
In the fourth test case, you can choose $$$k = 3$$$ and split the array into subsegments $$$(1, 2), (3, 5), (6, 6)$$$.
The split score is $$$\gcd(1 + 2, 1 + 1 + 1, 3) = 3$$$.
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