Codeforces Round 813 (Div. 2)
B
Woeful Permutation
Codeforces
800
原题
← AC →
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I wonder, does the falling rain

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*Forever yearn for it's disdain?*Effluvium of the Mind

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You are given a positive integer $n$.

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Find any permutation $p$ of length $n$ such that the sum $\operatorname{lcm}(1,p_1) + \operatorname{lcm}(2, p_2) + \ldots + \operatorname{lcm}(n, p_n)$ is as large as possible.

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Here $\operatorname{lcm}(x, y)$ denotes the least common multiple (LCM) of integers $x$ and $y$.

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A permutation is an array consisting of $n$ distinct integers from $1$ to $n$ in arbitrary order. For example, $[2,3,1,5,4]$ is a permutation, but $[1,2,2]$ is not a permutation ($2$ appears twice in the array) and $[1,3,4]$ is also not a permutation ($n=3$ but there is $4$ in the array).

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Input

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Each test contains multiple test cases. The first line contains the number of test cases $t$ ($1 \le t \le 1\,000$). Description of the test cases follows.

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The only line for each test case contains a single integer $n$ ($1 \le n \le 10^5$).

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

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Output

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For each test case print $n$ integers $p_1$, $p_2$, $\ldots$, $p_n$ — the permutation with the maximum possible value of $\operatorname{lcm}(1,p_1) + \operatorname{lcm}(2, p_2) + \ldots + \operatorname{lcm}(n, p_n)$.

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If there are multiple answers, print any of them.

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Note

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For $n = 1$, there is only one permutation, so the answer is $[1]$.

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For $n = 2$, there are two permutations:

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  • $[1, 2]$ — the sum is $\operatorname{lcm}(1,1) + \operatorname{lcm}(2, 2) = 1 + 2 = 3$.
  • $[2, 1]$ — the sum is $\operatorname{lcm}(1,2) + \operatorname{lcm}(2, 1) = 2 + 2 = 4$.
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样例

Input #1
2
1
2
Output #1
1
2 1
InputCopy OutputCopy
题目信息
题号
1712B
时间限制
1 s
内存限制
256 MB
标签
构造
贪心
数论

题面与样例版权归 Codeforces 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。