CF1530D.Secret Santa

Every December, VK traditionally holds an event for its employees named "Secret Santa". Here's how it happens.

$n$ employees numbered from $1$ to $n$ take part in the event. Each employee $i$ is assigned a different employee $b_i$, to which employee $i$ has to make a new year gift. Each employee is assigned to exactly one other employee, and nobody is assigned to themselves (but two employees may be assigned to each other). Formally, all $b_i$ must be distinct integers between $1$ and $n$, and for any $i$, $b_i \ne i$ must hold.

The assignment is usually generated randomly. This year, as an experiment, all event participants have been asked who they wish to make a gift to. Each employee $i$ has said that they wish to make a gift to employee $a_i$.

Find a valid assignment $b$ that maximizes the number of fulfilled wishes of the employees.

每年 12 月，VK 公司都会为其员工举办一项名为“秘密圣诞老人”的传统活动。活动规则如下：

共有 $n$ 名员工，编号从 $1$ 到 $n$。每名员工 $i$ 被分配给另一名不同的员工 $b_i$，即员工 $i$ 需要为员工 $b_i$ 准备新年礼物。每位员工恰好被分配给另一位员工，且任何人都不能被分配给自己（但两名员工可以互相分配）。形式化地说，所有 $b_i$ 必须是 $1$ 到 $n$ 之间互不相同的整数，且对任意 $i$，必须满足 $b_i \ne i$。

该分配通常随机生成。而今年，作为一项实验，所有活动参与者都被询问了他们希望将礼物送给谁。每名员工 $i$ 表示希望将礼物送给员工 $a_i$。

请找出一个合法的分配方案 $b$，使得员工愿望被满足的数量最大化。

Each test contains multiple test cases. The first line contains the number of test cases $t$ ($1 \le t \le 10^5$). Description of the test cases follows.

Each test case consists of two lines. The first line contains a single integer $n$ ($2 \le n \le 2 \cdot 10^5$) — the number of participants of the event.

The second line contains $n$ integers $a_1, a_2, \ldots, a_n$ ($1 \le a_i \le n$; $a_i \ne i$) — wishes of the employees in order from $1$ to $n$.

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

每个测试包含多个测试用例。第一行包含测试用例的数量 $t$（$1 \le t \le 10^5$）。随后是各测试用例的描述。

每个测试用例由两行组成。第一行包含一个整数 $n$（$2 \le n \le 2 \cdot 10^5$）—— 活动参与者的数量。

第二行包含 $n$ 个整数 $a_1, a_2, \ldots, a_n$（$1 \le a_i \le n$；$a_i \ne i$）—— 员工的愿望，按编号 $1$ 到 $n$ 的顺序给出。

保证所有测试用例的 $n$ 之和不超过 $2 \cdot 10^5$。

For each test case, print two lines.

In the first line, print a single integer $k$ ($0 \le k \le n$) — the number of fulfilled wishes in your assignment.

In the second line, print $n$ distinct integers $b_1, b_2, \ldots, b_n$ ($1 \le b_i \le n$; $b_i \ne i$) — the numbers of employees assigned to employees $1, 2, \ldots, n$.

$k$ must be equal to the number of values of $i$ such that $a_i = b_i$, and must be as large as possible. If there are multiple answers, print any.

对于每个测试用例，输出两行。

第一行，输出一个整数 $k$（$0 \le k \le n$）—— 表示你所构造的分配方案中满足的愿望数量。

第二行，输出 $n$ 个互不相同的整数 $b_1, b_2, \ldots, b_n$（$1 \le b_i \le n$；且 $b_i \ne i$）—— 表示分配给员工 $1, 2, \ldots, n$ 的员工编号。

其中 $k$ 必须等于满足 $a_i = b_i$ 的下标 $i$ 的个数，且应尽可能大。若存在多个合法答案，输出任意一个即可。

In the first test case, two valid assignments exist: $[3, 1, 2]$ and $[2, 3, 1]$. The former assignment fulfills two wishes, while the latter assignment fulfills only one. Therefore, $k = 2$, and the only correct answer is $[3, 1, 2]$.

在第一个测试用例中，存在两个有效的分配方案：$[3, 1, 2]$ 和 $[2, 3, 1]$。前一个分配方案满足了两个愿望，而后一个分配方案仅满足了一个愿望。因此，$k = 2$，唯一正确的答案是 $[3, 1, 2]$。