Optimize partitioning for in-place
Last updated: November 23, 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 given pivot are on one side and all elements greater than or equal to the pivot are on the other side. The function should modify the array directly and return the index of the pivot after partitioning.
Visa
November 23, 2025102
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2,755 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 given pivot are on one side and all elements greater than or equal to the pivot are on the other side. The function should modify the array directly and return the index of the pivot after partitioning.
Coding interviews at Visa 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
- Quickly identify the optimal approach and its theoretical basis
- Handle complex algorithm design with multiple interacting components
- Write concise, elegant code under time pressure
- Prove correctness of your approach and discuss alternative solutions
- Optimize beyond the obvious: discuss constant factor improvements
- Address follow-up variations and explain how the solution generalizes
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?
- Can you optimize the space complexity of your solution?
- What happens if the input contains duplicates?
- What is the worst-case input for your solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to partition an array such that all elements less than a given pivot are on one side, while all elements greater than or equal to the pivot are on the other side. This calls fo...
Approach
- Initialize Pointers: Start with two pointers,
leftat the beginning of the array andrightat the end. - Traverse the Array: Use a while loop to iterate until
leftis less than `rig...
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