A14605 | Make Them Equal

Theofanis has a string $s_1 s_2 \dots s_n$ and a character $c$ . He wants to make all characters of the string equal to $c$ using the minimum number of operations.

In one operation he can choose a number $x$ ( $1 \le x \le n$ ) and for every position $i$ , where $i$ is not divisible by $x$ , replace $s_i$ with $c$ .

Find the minimum number of operations required to make all the characters equal to $c$ and the $x$ -s that he should use in his operations.

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

The first line of each test case contains the integer $n$ ( $3 \le n \le 3 \cdot 10^5$ ) and a lowercase Latin letter $c$ — the length of the string $s$ and the character the resulting string should consist of.

The second line of each test case contains a string $s$ of lowercase Latin letters — the initial string.

It is guaranteed that the sum of $n$ over all test cases does not exceed $3 \cdot 10^5$ .

For each test case, firstly print one integer $m$ — the minimum number of operations required to make all the characters equal to $c$ .

Next, print $m$ integers $x_1, x_2, \dots, x_m$ ( $1 \le x_j \le n$ ) — the $x$ -s that should be used in the order they are given.

It can be proved that under given constraints, an answer always exists. If there are multiple answers, print any.