Topological Sort on graph
Last updated: March 23, 2026
Quick Overview
Given a directed acyclic graph (DAG), implement a function to perform a topological sort and return a linear ordering of its vertices. The input will be represented as an adjacency list, and the output should be a list of vertices in topologically sorted order. If the graph contains cycles, return an empty list.
Netflix
March 23, 20267
14
1,020 solved
Given a directed acyclic graph (DAG), implement a function to perform a topological sort and return a linear ordering of its vertices. The input will be represented as an adjacency list, and the output should be a list of vertices in topologically sorted order. If the graph contains cycles, return an empty list.
Coding interviews at Netflix 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
- 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 modify your solution to handle streaming input?
- What is the worst-case input for your solution?
- Can you solve this in a single pass?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to perform a topological sort on a directed acyclic graph (DAG). The key pattern that applies here is Depth-First Search (DFS) or Kahn's Algorithm (BFS). We will use the DFS ap...
Approach
- Initialize Structures: Create a stack to hold the topological ordering and a set to track visited nodes.
- DFS Function: Write a recursive function to visit nodes:
- If a node is al...
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