Number of permutation with K inversions
Submissions: 261   Accuracy:

36.78%

  Difficulty: Easy   Marks: 2

Given an array, an inversion is defined as a pair a[i], a[j] such that a[i] > a[j] and i < j. We are given two numbers N and k, we need to tell how many permutation of first N number have exactly K inversion.

Input:
The first line of input contains an integer T denoting the number of test cases. Then T test cases follow. The first line of each test case contains integers N and K.

Output:
Print the count of the number of permutations for the first N numbers which have exactly K inversions. Since the answer can be quite large print the answer modulo 109+7. Print the answer for each testcase in a new line.

Constraints:
1<= T <=100
1<= N, K <=100

Example:
Input:
1
3 1
Output:
2

Explanation :  
Total Permutation of first N number,
123, 132, 213, 231, 312, 321
Permutation with 1 inversion : 132 and 213

** For More Input/Output Examples Use 'Expected Output' option **

Contributor: Sujnesh Mishra
Author: sujnesh


If you have purchased any course from GeeksforGeeks then please ask your doubt on course discussion forum. You will get quick replies from GFG Moderators there.



Need help with your code? Please use ide.geeksforgeeks.org, generate link and share the link here.

to report an issue on this page.