Optimize rotation for O(1) space
Last updated: November 11, 2025
Quick Overview
Given a circular array, implement a function to rotate the array to the right by a specified number of steps while using O(1) additional space. The function should modify the array in place and return the rotated array as output. Ensure the solution efficiently handles cases where the number of steps exceeds the array's length.
SpaceX
November 11, 20254
12
1,009 solved
Given a circular array, implement a function to rotate the array to the right by a specified number of steps while using O(1) additional space. The function should modify the array in place and return the rotated array as output. Ensure the solution efficiently handles cases where the number of steps exceeds the array's length.
SpaceX uses this problem in the Technical Screen to evaluate your algorithmic thinking. They expect you to discuss multiple approaches, analyze trade-offs between them, and implement the optimal solution with clean, readable code.
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?
- What is the worst-case input for your solution?
- Can you optimize the space complexity of your solution?
- How would you parallelize this solution?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires rotating a circular array to the right by a specified number of steps using O(1) additional space, meaning we cannot use any additional data structures that grow with input size. ...
Approach
The algorithm can be broken down into the following steps:
- Normalize the Rotation Steps: Calculate the effective rotations needed using
k = k % n, wherenis the length of the array. - **...
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