Optimize rotation for with follow-up
Last updated: February 23, 2026
Quick Overview
Given an array of integers representing the rotation of a sorted array, write a function to optimize the rotation of the array by a specified number of positions. The function should take the array and the number of positions to rotate as inputs and return the rotated array. Ensure your solution operates in O(n) time complexity with O(1) space complexity.
Doordash
February 23, 20263
8
1,037 solved
Given an array of integers representing the rotation of a sorted array, write a function to optimize the rotation of the array by a specified number of positions. The function should take the array and the number of positions to rotate as inputs and return the rotated array. Ensure your solution operates in O(n) time complexity with O(1) space complexity.
Doordash uses this problem in the Take-home Project 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
- Identify the correct data structure and algorithm for the problem
- Write clean, bug-free code with proper variable naming
- Analyze time and space complexity correctly
- Handle basic edge cases (empty input, single element)
- Communicate your thought process while coding
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
- What if the input doesn't fit in memory?
- Can you solve this iteratively instead of recursively (or vice versa)?
- How would you test this solution thoroughly?
- What happens if the input contains duplicates?
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Practice DSA ProblemsSample Answer
Problem Analysis
This problem requires us to rotate a sorted array by a specified number of positions. The key observation here is that a rotation can be viewed as a combination of slicing the array into two parts and...
Approach
- Input Validation: Check if the input array is empty or has a single element, return it as is. If k is greater than the length of the array, compute
k = k % n. 2. Reverse the Whole Array: ...
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