Package g0601_0700.s0629_k_inverse_pairs_array

Class Solution

  • All Implemented Interfaces:
    
public final class Solution

    629 - K Inverse Pairs Array\.

    Hard

    For an integer array nums, an inverse pair is a pair of integers [i, j] where 0 <= i < j < nums.length and nums[i] > nums[j].

    Given two integers n and k, return the number of different arrays consist of numbers from 1 to n such that there are exactly k inverse pairs. Since the answer can be huge, return it modulo <code>10<sup>9</sup> + 7</code>.

    Example 1:

    Input: n = 3, k = 0

    Output: 1

    Explanation: Only the array 1,2,3 which consists of numbers from 1 to 3 has exactly 0 inverse pairs.

    Example 2:

    Input: n = 3, k = 1

    Output: 2

    Explanation: The array 1,3,2 and 2,1,3 have exactly 1 inverse pair.

    Constraints:

    • 1 &lt;= n &lt;= 1000

    • 0 &lt;= k &lt;= 1000

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description

    • Field Summary

      Fields 
      Modifier and Type Field Description

    • Constructor Summary

      Constructors 
      Constructor Description
      Solution()

    • Enum Constant Summary

      Enum Constants 
      Enum Constant Description

    • Method Summary

      Modifier and Type Method Description
      final Integer kInversePairs(Integer n, Integer k)

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait