CF1610B.Kalindrome Array

An array $[b_1, b_2, \ldots, b_m]$ is a palindrome, if $b_i = b_{m+1-i}$ for each $i$ from $1$ to $m$ . Empty array is also a palindrome.

An array is called kalindrome, if the following condition holds:

• It's possible to select some integer $x$ and delete some of the elements of the array equal to $x$ , so that the remaining array (after gluing together the remaining parts) is a palindrome.

Note that you don't have to delete all elements equal to $x$ , and you don't have to delete at least one element equal to $x$ .

For example :

• $[1, 2, 1]$ is kalindrome because you can simply not delete a single element.
• $[3, 1, 2, 3, 1]$ is kalindrome because you can choose $x = 3$ and delete both elements equal to $3$ , obtaining array $[1, 2, 1]$ , which is a palindrome.
• $[1, 2, 3]$ is not kalindrome.

You are given an array $[a_1, a_2, \ldots, a_n]$ . Determine if $a$ is kalindrome or not.

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

The first line of each test case contains a single integer $n$ ( $1 \le n \le 2 \cdot 10^5$ ) — the length of the array.

The second line of each test case contains $n$ integers $a_1, a_2, \ldots, a_n$ ( $1 \le a_i \le n$ ) — elements of the array.

It's guaranteed that the sum of $n$ over all test cases won't exceed $2 \cdot 10^5$ .

For each test case, print YES if $a$ is kalindrome and NO otherwise. You can print each letter in any case.

In the first test case, array $[1]$ is already a palindrome, so it's a kalindrome as well.

In the second test case, we can choose $x = 2$ , delete the second element, and obtain array $[1]$ , which is a palindrome.

In the third test case, it's impossible to obtain a palindrome.

In the fourth test case, you can choose $x = 4$ and delete the fifth element, obtaining $[1, 4, 4, 1]$ . You also can choose $x = 1$ , delete the first and the fourth elements, and obtain $[4, 4, 4]$ .