Optimize inversion for without recursion
Last updated: October 27, 2025
Quick Overview
Given an array of integers, write a function to optimize the calculation of 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]. Your function should return the total count of inversions in the array.
TikTok
October 27, 2025117
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Given an array of integers, write a function to optimize the calculation of 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]. Your function should return the total count of inversions in the array.
Coding interviews at TikTok focus on problem-solving approach as much as the final solution. The interviewer wants to see you break down the problem, consider edge cases, and optimize iteratively. Communication throughout the process is key.
What the Interviewer Expects
- Recognize the underlying problem pattern (sliding window, two pointers, BFS/DFS, etc.)
- Discuss multiple approaches and trade-offs before coding
- Implement an optimal solution with clean, production-quality code
- Handle all edge cases including boundary conditions and invalid input
- Optimize both time and space complexity with clear justification
- Test your solution systematically with well-chosen examples
Key Topics to Cover
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.
Possible Follow-up Questions
- How would you modify your solution to handle streaming input?
- What is the worst-case input for your solution?
- What happens if the input contains duplicates?
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Problem Analysis
To find the number of inversions in an array without recursion, we can utilize the concept of a modified merge sort algorithm. The problem specifically asks for an efficient way to count inversions, w...
Approach
- Initialization: Create a function
count_inversions(arr)that initializes a helper functionmerge_and_count(arr, temp_arr, left, mid, right). This will help in merging the two halves while c...
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