Package g0601_0700.s0629_k_inverse_pairs_array

Class Solution

java.lang.Object

g0601_0700.s0629_k_inverse_pairs_array.Solution

public class Solution
extends Object

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** 109 + 7. **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 <= n <= 1000` * `0 <= k <= 1000`

Constructor Summary

Constructors

Constructor	Description
Solution()

Method Summary

Modifier and Type	Method	Description
int	kInversePairs(int n, int k)

Methods inherited from class java.lang.Object

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

Constructor Details

Solution

public Solution()

Method Details

kInversePairs

public int kInversePairs(int n,
 int k)