Transform string to adjacency list
Last updated: November 5, 2025
Quick Overview
Given a string representation of a graph where each node is represented by a character and edges are denoted by pairs of characters, transform this string into an adjacency list. The output should be a dictionary where each key is a node and its value is a list of adjacent nodes. For example, for the input "a-b,c-d", the output should be {"a": ["b"], "b": ["a"], "c": ["d"], "d": ["c"]}.
Shopify
November 5, 202563
5
2,193 solved
Given a string representation of a graph where each node is represented by a character and edges are denoted by pairs of characters, transform this string into an adjacency list. The output should be a dictionary where each key is a node and its value is a list of adjacent nodes. For example, for the input "a-b,c-d", the output should be {"a": ["b"], "b": ["a"], "c": ["d"], "d": ["c"]}.
This coding problem is frequently asked during Technical Screen at Shopify. The interviewer is testing your ability to translate a problem into clean, working code while discussing time and space complexity. Shopify expects candidates to write production-quality code, not just solve the puzzle.
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
- Can you solve this iteratively instead of recursively (or vice versa)?
- What is the worst-case input for your solution?
- Can you optimize the space complexity of your solution?
- How would you test this solution thoroughly?
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Problem Analysis
The problem requires transforming a string representation of a graph into an adjacency list. The edges between nodes are represented as pairs of characters separated by a delimiter (like commas). The ...
Approach
- Initialize an empty dictionary to hold the adjacency list.
- Split the input string by commas to isolate each edge. For example, for "a-b,c-d", splitting by ',' gives ['a-b', 'c-d'].
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