Codeforces Round 842 (Div. 2)
D
Lucky Permutation
Codeforces
1800
原题
← CE →
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You are given a permutation$^\dagger$ $p$ of length $n$.

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In one operation, you can choose two indices $1 \le i \lt j \le n$ and swap $p_i$ with $p_j$.

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Find the minimum number of operations needed to have exactly one inversion$^\ddagger$ in the permutation.

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$^\dagger$ 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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$^\ddagger$ The number of inversions of a permutation $p$ is the number of pairs of indices $(i, j)$ such that $1 \le i \lt j \le n$ and $p_i \gt p_j$.

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Input

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

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The first line of each test case contains a single integer $n$ ($2 \le n \le 2 \cdot 10^5$).

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The second line of each test case contains $n$ integers $p_1,p_2,\ldots, p_n$ ($1 \le p_i \le n$). It is guaranteed that $p$ is a permutation.

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It is guaranteed that the sum of $n$ over all test cases does not exceed $2 \cdot 10^5$.

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Output

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For each test case output a single integer — the minimum number of operations needed to have exactly one inversion in the permutation. It can be proven that an answer always exists.

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Note

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In the first test case, the permutation already satisfies the condition.

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In the second test case, you can perform the operation with $(i,j)=(1,2)$, after that the permutation will be $[2,1]$ which has exactly one inversion.

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In the third test case, it is not possible to satisfy the condition with less than $3$ operations. However, if we perform $3$ operations with $(i,j)$ being $(1,3)$,$(2,4)$, and $(3,4)$ in that order, the final permutation will be $[1, 2, 4, 3]$ which has exactly one inversion.

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In the fourth test case, you can perform the operation with $(i,j)=(2,4)$, after that the permutation will be $[2,1,3,4]$ which has exactly one inversion.

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样例

Input #1
4
2
2 1
2
1 2
4
3 4 1 2
4
2 4 3 1
Output #1
0
1
3
1
InputCopy OutputCopy
题目信息
题号
1768D
时间限制
1 s
内存限制
256 MB
标签
构造
DFS 及类似
图论
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。