Find shortest distance in graph
Last updated: September 13, 2025
Quick Overview
Given a weighted, undirected graph represented as an adjacency list, write a function to find the shortest distance from a starting node to all other nodes using Dijkstra's algorithm. The function should return a list of distances, where the index corresponds to the node number, and the distance is represented as an integer. If a node is unreachable, return -1 for that node.
Citadel
September 13, 202531
3
1,718 solved
Given a weighted, undirected graph represented as an adjacency list, write a function to find the shortest distance from a starting node to all other nodes using Dijkstra's algorithm. The function should return a list of distances, where the index corresponds to the node number, and the distance is represented as an integer. If a node is unreachable, return -1 for that node.
Citadel uses this problem in the Technical 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?
- What happens if the input contains duplicates?
- How would your solution change if the input was sorted?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to find the shortest distances from a starting node to all other nodes in a weighted, undirected graph. This is a classic shortest path problem that can be efficiently solved u...
Approach
- Initialize Data Structures: Create a list
distancesinitialized to infinity (float('inf')) for each node, except for the starting node which is set to 0. Use a priority queue (min-heap) to ...
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