Transform matrix to adjacency list
Last updated: June 1, 2026
Quick Overview
Given a matrix representation of a graph where each element indicates the presence of an edge between nodes, transform this matrix into an adjacency list format. The input will be a 2D array where `matrix[i][j]` is 1 if there is an edge from node `i` to node `j`, and 0 otherwise. The output should be a list of lists, where each inner list contains the neighbors of the corresponding node.
Roblox
June 1, 20264
14
3,605 solved
Given a matrix representation of a graph where each element indicates the presence of an edge between nodes, transform this matrix into an adjacency list format. The input will be a 2D array where `matrix[i][j]` is 1 if there is an edge from node `i` to node `j`, and 0 otherwise. The output should be a list of lists, where each inner list contains the neighbors of the corresponding node.
Roblox 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
- 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 solve this in a single pass?
- How would you parallelize this solution?
- How would you modify your solution to handle streaming input?
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Problem Analysis
The problem involves transforming a matrix representation of a graph into an adjacency list format. The matrix is a 2D array where each element matrix[i][j] indicates the presence (1) or absence (...
Approach
- Initialize an empty list called
adjacency_listto store the neighbors for each node. - Iterate through each row of the matrix with an index
irepresenting the current node. - For each node ...
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