Optimize rotation for O(1) space
Last updated: May 18, 2026
Quick Overview
Given an array representing a list of elements, implement a function to rotate the array to the right by a given number of steps, ensuring that the solution uses O(1) space. The function should modify the array in place and return nothing, with the input being the array and the number of steps as an integer.
Waymo
May 18, 20267
16
1,646 solved
Given an array representing a list of elements, implement a function to rotate the array to the right by a given number of steps, ensuring that the solution uses O(1) space. The function should modify the array in place and return nothing, with the input being the array and the number of steps as an integer.
Waymo uses this problem in the Onsite 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
- 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?
- Can you optimize the space complexity of your solution?
- What happens if the input contains duplicates?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to rotate an array to the right by a given number of steps while modifying the array in place and using O(1) space. The key pattern here is the Reverse Array technique, whi...
Approach
The approach involves three main steps:
- Normalize the number of steps to avoid unnecessary rotations (if k is greater than the length of the array, we only need to rotate by k % n).
- **Revers...
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