Optimize inversion for without recursion
Last updated: September 19, 2025
Quick Overview
Given an array of integers, implement a function to count the number of inversions in the array without using recursion. An inversion is defined as a pair of indices (i, j) such that i < j and arr[i] > arr[j]. The function should return the total count of inversions in O(n log n) time complexity.
Walmart
September 19, 2025160
12
4,678 solved
Given an array of integers, implement a function to count the number of inversions in the array without using recursion. An inversion is defined as a pair of indices (i, j) such that i < j and arr[i] > arr[j]. The function should return the total count of inversions in O(n log n) time complexity.
How to Approach This
- Clarify input constraints and edge cases before writing code.
- Walk through your approach verbally and confirm with the interviewer before coding.
- Start with a brute force solution, then optimize. Mention time and space complexity.
- Test your solution with examples, including edge cases like empty input or duplicates.
- Consider common patterns: sliding window, two pointers, hash map, BFS/DFS, dynamic programming.
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Problem Analysis
To count the number of inversions in an array efficiently, we can utilize a modified merge sort algorithm. The reason this approach is suitable is that during the merge step of the merge sort, we can ...
Approach
- Merge Sort Algorithm: We will implement a merge sort function that sorts the array while counting inversions.
- Counting Inversions: During the merge step, when an element from the right h...
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