Codeforces Round 696 (Div. 2)
E
What Is It?
Codeforces
2500
原题
← DF →
翻译中…

Lunar rover finally reached planet X. After landing, he met an obstacle, that contains permutation $p$ of length $n$. Scientists found out, that to overcome an obstacle, the robot should make $p$ an identity permutation (make $p_i = i$ for all $i$).

翻译中…

Unfortunately, scientists can't control the robot. Thus the only way to make $p$ an identity permutation is applying the following operation to $p$ multiple times:

翻译中…
  • Select two indices $i$ and $j$ ($i \neq j$), such that $p_j = i$ and swap the values of $p_i$ and $p_j$. It takes robot $(j - i)^2$ seconds to do this operation.
翻译中…

Positions $i$ and $j$ are selected by the robot (scientists can't control it). He will apply this operation while $p$ isn't an identity permutation. We can show that the robot will make no more than $n$ operations regardless of the choice of $i$ and $j$ on each operation.

翻译中…

Scientists asked you to find out the maximum possible time it will take the robot to finish making $p$ an identity permutation (i. e. worst-case scenario), so they can decide whether they should construct a new lunar rover or just rest and wait. They won't believe you without proof, so you should build an example of $p$ and robot's operations that maximizes the answer.

翻译中…

For a better understanding of the statement, read the sample description.

翻译中…

Input

翻译中…

The first line of input contains a single integer $t$ ($1 \leq t \leq 10^4$) — the number of test cases.

翻译中…

Each of next $t$ lines contains the single integer $n$ ($2 \leq n \leq 10^5$) – the length of $p$.

翻译中…

Note, that $p$ is not given to you. You should find the maximum possible time over all permutations of length $n$.

翻译中…

It is guaranteed, that the total sum of $n$ over all test cases doesn't exceed $10^5$.

翻译中…

Output

翻译中…

For each test case in the first line, print how many seconds will the robot spend in the worst case.

翻译中…

In the next line, print the initial value of $p$ that you used to construct an answer.

翻译中…

In the next line, print the number of operations $m \leq n$ that the robot makes in your example.

翻译中…

In the each of next $m$ lines print two integers $i$ and $j$ — indices of positions that the robot will swap on this operation. Note that $p_j = i$ must holds (at the time of operation).

翻译中…

Note

翻译中…

For $n = 2$, $p$ can be either $[1, 2]$ or $[2, 1]$. In the first case $p$ is already identity, otherwise robot will make it an identity permutation in $1$ second regardless of choise $i$ and $j$ on the first operation.

翻译中…

For $n = 3$, $p$ can be equals $[2, 3, 1]$.

翻译中…
  • If robot will select $i = 3, j = 2$ on the first operation, $p$ will become $[2, 1, 3]$ in one second. Now robot can select only $i = 1, j = 2$ or $i = 2, j = 1$. In both cases, $p$ will become identity in one more second ($2$ seconds in total).
  • If robot will select $i = 1, j = 3$ on the first operation, $p$ will become $[1, 3, 2]$ in four seconds. Regardless of choise of $i$ and $j$ on the second operation, $p$ will become identity in five seconds.
翻译中…

We can show, that for permutation of length $3$ robot will always finish all operation in no more than $5$ seconds.

翻译中…

样例

Input #1
3
2
3
3
Output #1
1
2 1
1
2 1
5
2 3 1
2
1 3
3 2
5
2 3 1
2
1 3
2 3
InputCopy OutputCopy
题目信息
题号
1474E
时间限制
1 s
内存限制
256 MB
标签
构造
贪心

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。