CF1895F.Fancy Arrays
普及/提高-
通过率:0%
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题目描述
Let's call an array a of n non-negative integers fancy if the following conditions hold:
- at least one from the numbers x , x+1 , ..., x+k−1 appears in the array;
- consecutive elements of the array differ by at most k (i.e. ∣ai−ai−1∣≤k for each i∈[2,n] ).
You are given n , x and k . Your task is to calculate the number of fancy arrays of length n . Since the answer can be large, print it modulo 109+7 .
输入格式
The first line contains a single integer t ( 1≤t≤50 ) — the number of test cases.
The only line of each test case contains three integers n , x and k ( 1≤n,k≤109 ; 0≤x≤40 ).
输出格式
For each test case, print a single integer — the number of fancy arrays of length n , taken modulo 109+7 .
输入输出样例
输入#1
4 3 0 1 1 4 25 4 7 2 1000000000 40 1000000000
输出#1
9 25 582 514035484
说明/提示
In the first test case of the example, the following arrays are fancy:
- [0,0,0] ;
- [0,0,1] ;
- [0,1,0] ;
- [0,1,1] ;
- [0,1,2] ;
- [1,0,0] ;
- [1,0,1] ;
- [1,1,0] ;
- [2,1,0] .