Codeforces Global Round 27 |
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Finished |
Alya has been given a hard problem. Unfortunately, she is too busy running for student council. Please solve this problem for her.
Given an integer $$$n$$$, construct a permutation $$$p$$$ of integers $$$1, 2, \ldots, n$$$ that maximizes the value of $$$k$$$ (which is initially $$$0$$$) after the following process.
Perform $$$n$$$ operations, on the $$$i$$$-th operation ($$$i=1, 2, \dots, n$$$),
The first line contains a single integer $$$t$$$ ($$$1\le t\le 500$$$) — the number of test cases.
The only line of each test case contains a single integer $$$n$$$ ($$$5\le n\le 2 \cdot 10^5$$$) — the length of the permutation.
It is guaranteed that the sum of $$$n$$$ over all test cases does not exceed $$$2 \cdot 10^5$$$.
For each test case, output the maximum value of $$$k$$$ in the first line and output the permutation $$$p_1, p_2,\ldots, p_n$$$ in the second line.
If there are multiple such permutations, output any.
65678910
5 2 1 3 4 5 7 1 2 4 6 5 3 7 2 4 5 1 3 6 7 15 2 4 5 1 3 6 7 8 9 2 4 5 6 7 1 3 8 9 15 1 2 3 4 5 6 8 10 9 7
For the first test case, the value of $$$k$$$ is determined as follows:
$$$k = 0$$$ initially.
The final value of $$$k$$$ is $$$5$$$. It can be shown that the final value of $$$k$$$ is at most $$$5$$$ for all permutations of length $$$5$$$. Another valid output is $$$[2, 3, 1, 4, 5]$$$.
For the second test case, the final value of $$$k$$$ is $$$7$$$. It can be shown that the final value of $$$k$$$ is at most $$$7$$$ for all permutations of length $$$6$$$. Other valid outputs include $$$[2, 4, 1, 6, 3, 5]$$$ and $$$[5, 2, 6, 1, 3, 4]$$$.
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