Permutation Addicts

Description:

Input:

Each test contains multiple test cases. The first line contains an integer $$$t$$$ ($$$1 \leq t \leq 10^5$$$) — the number of test cases. The following lines contain the description of each test case.

The first line of each test case contains an integer $$$n$$$ ($$$1 \leq n \leq 10^5$$$), indicating the length of the permutation $$$a$$$.

The second line of each test case contains $$$n$$$ integers $$$b_1, b_2, \dots, b_n$$$ ($$$0 \leq b_i \leq n+1$$$), indicating the elements of the sequence $$$b$$$.

It is guaranteed that there exists at least one pair of permutation $$$a_1, a_2, \dots, a_n$$$ and threshold $$$k$$$ that produce the sequence $$$b_1, b_2, \dots, b_n$$$.

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

Output:

For each test case, output the threshold $$$k$$$ ($$$0 \leq k \leq n$$$) in the first line, and then output the permutation $$$a_1, a_2, \dots, a_n$$$ ($$$1 \leq a_i \leq n$$$) in the second line such that the permutation $$$a_1, a_2, \dots, a_n$$$ and threshold $$$k$$$ produce the sequence $$$b_1, b_2, \dots, b_n$$$. If there are multiple solutions, you can output any of them.

Sample Input:

3
4
5 3 1 2
6
7 7 7 3 3 3
6
4 4 4 0 0 0

Sample Output:

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

Note:

For the first test case, permutation $$$a = [1,3,2,4]$$$ and threshold $$$k = 2$$$ will produce sequence $$$b$$$ as follows.

• When $$$i = 1$$$, $$$x = a_i = 1 \leq k$$$, there is no $$$a_j$$$ ($$$1 \leq j < i$$$) that $$$a_j > k$$$. Therefore, $$$b_1 = n + 1 = 5$$$.
• When $$$i = 2$$$, $$$x = a_i = 3 > k$$$, the last element $$$a_j$$$ that $$$a_j \leq k$$$ is $$$a_1$$$. Therefore, $$$b_3 = a_1 = 1$$$.
• When $$$i = 3$$$, $$$x = a_i = 2 \leq k$$$, the last element $$$a_j$$$ that $$$a_j > k$$$ is $$$a_2$$$. Therefore, $$$b_2 = a_2 = 3$$$.
• When $$$i = 4$$$, $$$x = a_i = 4 > k$$$, the last element $$$a_j$$$ that $$$a_j \leq k$$$ is $$$a_3$$$. Therefore, $$$b_4 = a_3 = 2$$$.

Finally, we obtain sequence $$$b = [5,3,1,2]$$$.

For the second test case, permutation $$$a = [1,2,3,4,5,6]$$$ and threshold $$$k = 3$$$ will produce sequence $$$b$$$ as follows.

• When $$$i = 1, 2, 3$$$, $$$a_i \leq k$$$, there is no $$$a_j$$$ ($$$1 \leq j < i$$$) that $$$a_j > k$$$. Therefore, $$$b_1 = b_2 = b_3 = n + 1 = 7$$$.
• When $$$i = 4, 5, 6$$$, $$$a_i > k$$$, the last element $$$a_j$$$ that $$$a_j \leq k$$$ is $$$a_3$$$. Therefore, $$$b_4 = b_5 = b_6 = a_3 = 3$$$.

Finally, we obtain sequence $$$b = [7,7,7,3,3,3]$$$.

For the third test case, permutation $$$a = [6,5,4,3,2,1]$$$ and threshold $$$k = 3$$$ will produce sequence $$$b$$$ as follows.

• When $$$i = 1, 2, 3$$$, $$$a_i > k$$$, there is no $$$a_j$$$ ($$$1 \leq j < i$$$) that $$$a_j \leq k$$$. Therefore, $$$b_4 = b_5 = b_6 = 0$$$.
• When $$$i = 4, 5, 6$$$, $$$a_i \leq k$$$, the last element $$$a_j$$$ that $$$a_j > k$$$ is $$$a_3$$$. Therefore, $$$b_1 = b_2 = b_3 = a_3 = 4$$$.

Finally, we obtain sequence $$$b = [4,4,4,0,0,0]$$$.