27459번 - Adjacent Pairs 서브태스크다국어

Let's call an array $b_1, b_2, \dots , b_m$ good, if $b_i ≠ b_{i+1}$ for any $i$ with $1 ≤ i ≤ m - 1$.

You are given a good array of $n$ positive integers $a_1, a_2 , a_3 , \dots , a_n$.

You can perform the following operations on this array:

Choose any index $i$ ($1 ≤ i ≤ n$) and a number $x$ ($1 ≤ x ≤ 10^9$). Then, set $a_i$ to $x$. After this operation, the array has to remain good.

You want to perform several operations so that the resulting array will contain exactly two distinct values. Determine the smallest number of operations needed to achieve this goal.

The first line of input contains the integer $t$ ($1 ≤ t ≤ 10^5$), the number of test cases. The description of test cases follows.

The first line of each test case contains a single integer $n$ ($2 ≤ n ≤ 2 ⋅ 10^5$) - the length of the array.

The second line of each test case contains $n$ integers $a_1 , a_2 , \dots , a_n$ ($1 ≤ a_i ≤ n$) - elements of the array. It's guaranteed that $a_i ≠ a_{i+1}$ for $1 ≤ i ≤ n - 1$ (that is, the array is good).

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

For each test case, output a single integer - the smallest number of operations needed to achieve an array in which there are exactly two distinct values.

In the first test case, one of the optimal sequences of operations is:

$(4, 5, 2, 4, 5) → (2, 5, 2, 4, 5) → (2, 5, 2, 4, 2) → (2, 5, 2, 5, 2)$.

In the second test case, the array already contains only two distinct values, so the answer is $0$.