Topological Sort on graph
Last updated: October 19, 2025
Quick Overview
Given a directed acyclic graph (DAG), implement a function to perform a topological sort and return the nodes in a linear order such that for every directed edge from node A to node B, node A comes before node B in the ordering. The input will be represented as a list of edges, and the output should be a list of nodes in topologically sorted order.
Microsoft
October 19, 20259
6
929 solved
Given a directed acyclic graph (DAG), implement a function to perform a topological sort and return the nodes in a linear order such that for every directed edge from node A to node B, node A comes before node B in the ordering. The input will be represented as a list of edges, and the output should be a list of nodes in topologically sorted order.
Microsoft uses this problem in the Onsite 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
- 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 if the input doesn't fit in memory?
- How would you parallelize this solution?
- How would your solution change if the input was sorted?
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Practice DSA ProblemsSample Answer
Problem Analysis
To solve the problem of performing a topological sort on a directed acyclic graph (DAG), we can utilize the Kahn's algorithm, which employs the concept of in-degrees and a queue. A topological sort is...
Approach
- Initialize Data Structures: Create an in-degree dictionary to count incoming edges for each node and a list to hold the result of the topological sort. Also, create a queue to manage nodes with...
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