Find minimum cost in graph
Last updated: September 16, 2025
Quick Overview
Given a weighted, directed graph represented as an adjacency list, write a function to find the minimum cost to travel from a specified source node to a target node. The function should return the minimum cost as an integer, and if the target node is unreachable, return -1.
Plaid
September 16, 2025106
8
4,021 solved
Given a weighted, directed graph represented as an adjacency list, write a function to find the minimum cost to travel from a specified source node to a target node. The function should return the minimum cost as an integer, and if the target node is unreachable, return -1.
Plaid 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
- 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)?
- How would you modify your solution to handle streaming input?
- Can you solve this in a single pass?
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Practice DSA ProblemsSample Answer
Problem Analysis
The problem requires us to find the minimum cost to travel from a source node to a target node in a weighted directed graph. Here, the best-suited algorithm is Dijkstra's algorithm, which efficiently ...
Approach
- Initialize a priority queue: Use a min-heap to always extend the least cost path first.
- Track costs: Create a dictionary to store the minimum cost to reach each node, initialized with ...
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