Optimize rotation for with follow-up
Last updated: June 14, 2026
Quick Overview
Given a 2D matrix representing an image, rotate the matrix 90 degrees clockwise in place. The function should modify the input matrix directly and return nothing. The matrix is guaranteed to be n x n, where n is a positive integer.
xAI
June 14, 202635
6
1,485 solved
Given a 2D matrix representing an image, rotate the matrix 90 degrees clockwise in place. The function should modify the input matrix directly and return nothing. The matrix is guaranteed to be n x n, where n is a positive integer.
Coding interviews at xAI 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
- What happens if the input contains duplicates?
- Can you optimize the space complexity of your solution?
- Can you solve this in a single pass?
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Practice DSA ProblemsSample Answer
Problem Analysis
To rotate a square matrix 90 degrees clockwise, we can utilize a layer-by-layer approach, which is a specific application of the two-pointer technique. The matrix can be visualized as being made of co...
Approach
- Identify the number of layers in the matrix:
n // 2wherenis the dimension of the matrix. - For each layer, perform the following operations:
- Set the top-left corner of the layer as th...
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