Transform linked list to adjacency list
Last updated: December 10, 2025
Quick Overview
Given a singly linked list where each node contains a value and a reference to its next node, transform the linked list into an adjacency list representation of a graph. Each node's value should serve as a key in the adjacency list, with its corresponding value being a list of all connected nodes (i.e., nodes that can be reached from the current node). The output should be a dictionary where each key is a node's value and the value is a list of adjacent node values.
Salesforce
December 10, 20254
15
268 solved
Given a singly linked list where each node contains a value and a reference to its next node, transform the linked list into an adjacency list representation of a graph. Each node's value should serve as a key in the adjacency list, with its corresponding value being a list of all connected nodes (i.e., nodes that can be reached from the current node). The output should be a dictionary where each key is a node's value and the value is a list of adjacent node values.
Salesforce uses this problem in the Phone 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 you test this solution thoroughly?
- Can you solve this in a single pass?
- Can you solve this iteratively instead of recursively (or vice versa)?
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Practice DSA ProblemsSample Answer
Problem Analysis
In this problem, we need to convert a singly linked list into an adjacency list representation of a graph. The crucial observation here is that the linked list itself can be seen as a linear graph whe...
Approach
- Initialize a Dictionary: Create an empty dictionary to hold our adjacency list.
- Traverse the Linked List: Use a pointer to traverse the linked list starting from the head.
- **Build the...
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