Transform matrix to adjacency list
Last updated: September 19, 2025
Quick Overview
Given a matrix representation of a graph, transform it into an adjacency list format. The input will be a 2D array where each element indicates the presence of an edge between nodes. Your output should be a list of lists, where each sublist contains the neighbors of the corresponding node.
Square/Block
September 19, 20257
8
1,012 solved
Given a matrix representation of a graph, transform it into an adjacency list format. The input will be a 2D array where each element indicates the presence of an edge between nodes. Your output should be a list of lists, where each sublist contains the neighbors of the corresponding node.
Coding interviews at Square/Block 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
- 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
- Can you optimize the space complexity of your solution?
- What is the worst-case input for your solution?
- What if the input doesn't fit in memory?
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Problem Analysis
To transform a matrix representation of a graph into an adjacency list, we recognize that the matrix is a 2D array where the presence of an edge between nodes is indicated by non-zero values (typicall...
Approach
- Initialize an empty list called
adjacency_listwith a size equal to the number of nodes (length of the matrix). This will hold the neighbors for each node. - Loop through each index
ifrom 0 t...
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