题目描述
You are given two arrays $a$ and $b$ each consisting of $n$ integers. All elements of $a$ are pairwise distinct.
Find the number of ways to reorder $a$ such that $a_i > b_i$ for all $1 \le i \le n$, modulo $10^9 + 7$.
Two ways of reordering are considered different if the resulting arrays are different.
Input
Each test contains multiple test cases. The first line contains the number of test cases $t$ ($1 \le t \le 10^4$). The description of the test cases follows.
The first line of each test case contains a single integer $n$ ($1 \le n \le 2 \cdot 10^{5}$) — the length of the array $a$ and $b$.
The second line of each test case contains $n$ distinct integers $a_1$, $a_2$, $\ldots$, $a_n$ ($1 \le a_i \le 10^9$) — the array $a$. It is guaranteed that all elements of $a$ are pairwise distinct.
The second line of each test case contains $n$ integers $b_1$, $b_2$, $\ldots$, $b_n$ ($1 \le b_i \le 10^9$) — the array $b$.
It is guaranteed that the sum of $n$ over all test cases does not exceed $2 \cdot 10^{5}$.
Output
For each test case, output the number of ways to reorder array $a$ such that $a_i > b_i$ for all $1 \le i \le n$, modulo $10^9 + 7$.
输入格式
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输出格式
见题面 Output 部分