Optimize partitioning for in-place
Last updated: September 29, 2025
Quick Overview
Given an array of integers, implement an in-place algorithm to optimize the partitioning of the array such that all elements less than a specified pivot are moved to the left, and all elements greater than or equal to the pivot are moved to the right. The function should return the rearranged array while maintaining the relative order of the elements within each partition.
Anduril
September 29, 202592
12
969 solved
Given an array of integers, implement an in-place algorithm to optimize the partitioning of the array such that all elements less than a specified pivot are moved to the left, and all elements greater than or equal to the pivot are moved to the right. The function should return the rearranged array while maintaining the relative order of the elements within each partition.
Coding interviews at Anduril 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 your solution change if the input was sorted?
- What happens if the input contains duplicates?
- Can you solve this in a single pass?
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Problem Analysis
The problem requires us to partition an array of integers in-place based on a specified pivot. The goal is to rearrange the array such that all elements less than the pivot are on the left, while all ...
Approach
- Initialize two pointers:
leftstarting at the beginning of the array andrightat the end. - Use a list,
less_than_pivot, to collect elements less than the pivot and another list, `greater_...
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