CF1550D.Excellent Arrays
普及/提高-
通过率:0%
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题目描述
Let's call an integer array a1,a2,…,an good if ai=i for each i .
Let F(a) be the number of pairs (i,j) ( 1≤i<j≤n ) such that ai+aj=i+j .
Let's say that an array a1,a2,…,an is excellent if:
- a is good;
- l≤ai≤r for each i ;
- F(a) is the maximum possible among all good arrays of size n .
Given n , l and r , calculate the number of excellent arrays modulo 109+7 .
输入格式
The first line contains a single integer t ( 1≤t≤1000 ) — the number of test cases.
The first and only line of each test case contains three integers n , l , and r ( 2≤n≤2⋅105 ; −109≤l≤1 ; n≤r≤109 ).
It's guaranteed that the sum of n doesn't exceed 2⋅105 .
输出格式
For each test case, print the number of excellent arrays modulo 109+7 .
输入输出样例
输入#1
4 3 0 3 4 -3 5 42 -33 55 69 -42 146
输出#1
4 10 143922563 698570404
说明/提示
In the first test case, it can be proven that the maximum F(a) among all good arrays a is equal to 2 . The excellent arrays are:
- [2,1,2] ;
- [0,3,2] ;
- [2,3,2] ;
- [3,0,1] .