Minimum Coins to Reach an Amount

1. Problem Statement

You are given a list of coin denominations and a target amount. Each denomination has unlimited supply. Find the minimum number of coins needed to make exactly the target amount, or -1 if it cannot be made.

2. Live Coding Format

Work in the provided coding workspace while explaining your decisions to the live interviewer. Validation may use inline tests, examples, comments, or a verbal walkthrough.

3. Key Focus Areas

1
Problem clarification and contract
2
Approach exploration and optimality
3
Think-aloud communication and pacing
4
Implementation correctness
5
Code quality and language fluency
6
Tests and dry run
7
Debugging and self-correction
8
Complexity analysis
9
Follow-up performance

4. What Strong Candidates Should Demonstrate

Clarify coin supply, denomination properties, and impossible-case behavior before coding.
Explain a naive baseline, identify the repeated work, and improve it to a polynomial-time solution.
Think aloud while implementing readable, correct code.
Validate with explicit expected outputs and a top-to-bottom dry run.
Analyze time and space complexity and handle a bounded follow-up modification.

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Practice this problem in the live coding workspace while the interviewer probes your clarification, implementation, trade-offs, and validation.

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Core Concepts

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