How do you solve K Inverse Pairs Array on LeetCode?

K Inverse Pairs Array (LeetCode #629) can be solved using Brute Force. The optimal approach is Brute Force with undefined time complexity and undefined space complexity. Key insight: The brute force approach generates all possible permutations of the array and counts the number of inverse pairs in each permutation. This is straightforward but inefficient for larger values of n.

What is the time complexity of K Inverse Pairs Array?

The optimal solution for K Inverse Pairs Array runs in undefined time and uses undefined space. undefined

What algorithm or data structure is used to solve K Inverse Pairs Array?

K Inverse Pairs Array uses the following concepts: Dynamic Programming. The recommended patterns to study are: .

#629

K Inverse Pairs Array

Hard

Dynamic Programming

LeetCode ↗

Approaches

💡

Intuition

Time Space

The brute force approach generates all possible permutations of the array and counts the number of inverse pairs in each permutation. This is straightforward but inefficient for larger values of n.

⚙️

Algorithm

3 steps

1Step 1: Generate all permutations of the array containing numbers from 1 to n.
2Step 2: For each permutation, count the number of inverse pairs.
3Step 3: Return the count of permutations that have exactly k inverse pairs.

solution.py17 lines

1# Full working Python code
2from itertools import permutations
3
4def countInversePairs(n, k):
5    def count_pairs(arr):
6        count = 0
7        for i in range(len(arr)):
8            for j in range(i + 1, len(arr)):
9                if arr[i] > arr[j]:
10                    count += 1
11        return count
12
13    count = 0
14    for perm in permutations(range(1, n + 1)):
15        if count_pairs(perm) == k:
16            count += 1
17    return count % (10**9 + 7)

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.