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Problem: K Inverse Pairs Array

med
30 min
Try to solve the K Inverse Pairs Array problem.

Statement

Given two integers n and k, return the number of distinct arrays consisting of integers from 11 to n that contain exactly k inverse pairs. Since the answer can be very large, return it modulo 109+710^9 + 7.

An inverse pair in an array nums is defined as a pair of indices (i,j)(i, j) such that 0≤i<j<0 \leq i < j < nums.length and nums[i] >> nums[j].

Constraints:

  • 1≤1 \leq n ≤1000\leq 1000

  • 0≤0 \leq k ≤1000\leq 1000

⋮
Tap here to switch tabs
Problem
Submissions

Problem: K Inverse Pairs Array

med
30 min
Try to solve the K Inverse Pairs Array problem.

Statement

Given two integers n and k, return the number of distinct arrays consisting of integers from 11 to n that contain exactly k inverse pairs. Since the answer can be very large, return it modulo 109+710^9 + 7.

An inverse pair in an array nums is defined as a pair of indices (i,j)(i, j) such that 0≤i<j<0 \leq i < j < nums.length and nums[i] >> nums[j].

Constraints:

  • 1≤1 \leq n ≤1000\leq 1000

  • 0≤0 \leq k ≤1000\leq 1000