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] $ .