D. Secret Santa
time limit per test
2 seconds
memory limit per test
512 megabytes
standard input
standard output

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.


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 $$$2 \cdot 10^5$$$.


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.

2 1 2
6 4 6 2 4 5 6
3 1 2
6 4 7 2 3 5 1

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 $$$[3, 1, 2]$$$.