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How to Solve Design an ATM Machine Problem
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Start Free for WindowsMedium#2241
LeetCode ProblemDesign an ATM Machine
There is an ATM machine that stores banknotes of 5 denominations: 20, 50, 100, 200, and 500 dollars. Initially the ATM is empty. The user can use the machine to deposit or withdraw any amount of money. When withdrawing, the machine prioritizes using banknotes of larger values. Implement the ATM class:
ArrayGreedyDesign
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Problem Breakdown
Understanding the Design an ATM Machine Problem
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Problem Statement
There is an ATM machine that stores banknotes of 5 denominations: 20, 50, 100, 200, and 500 dollars. Initially the ATM is empty. The user can use the machine to deposit or withdraw any amount of money. When withdrawing, the machine prioritizes using banknotes of larger values. Implement the ATM class:
MediumProblem #2241
LeetCodeDesign an ATM Machine
Related Topics
ArrayGreedyDesign
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Examples
# Example 1
Input
—
Output
—
Constraints
banknotesCount.length == 5
0 <= banknotesCount[i] <= 109
1 <= amount <= 109
At most 5000 calls in total will be made to withdraw and deposit.
At least one call will be made to each function withdraw and deposit.
Sum of banknotesCount[i] in all deposits doesn't exceed 109
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Solve Design an ATM Machine — There is an ATM machine that stores banknotes of 5 denominations: 20, 50, 100, 2...
Here's the optimal approach using Array:
def solve(input):
# Optimal O(n) solution
return result
Time: O(n) | Space: O(n)
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Frequently Asked Questions
Common questions about solving Design an ATM Machine and using Phantom Code during coding interviews.
How does Phantom Code help me solve coding problems like Design an ATM Machine during interviews?
Phantom Code generates complete solutions instantly with proper complexity analysis, letting you focus on explaining your approach and demonstrating problem-solving skills rather than getting stuck on implementation details during high-pressure situations.
What if the interviewer asks follow-up questions or modifications to problems like Design an ATM Machine?
Phantom Code adapts in real-time. Screenshot the modified problem or use audio mode to capture the interviewer's follow-up, and get an updated solution within seconds — including edge cases and optimizations.
Can Phantom Code help me communicate my solution for problems like Design an ATM Machine?
Yes. Phantom Code provides step-by-step approach explanations with 3 progressive thoughts, so you can walk through your solution naturally. It also provides time and space complexity analysis to discuss trade-offs.
How does Phantom Code assist with different programming languages for Design an ATM Machine type problems?
Phantom Code supports 11 programming languages including Python, Java, C++, JavaScript, TypeScript, Go, Rust, Ruby, Swift, Kotlin, and C#. Set your preferred language and get idiomatic solutions.
What coding mistakes does Phantom Code help me avoid during Design an ATM Machine interviews?
Phantom Code catches common mistakes like off-by-one errors, missing edge cases, incorrect base conditions, and suboptimal approaches. It provides clean, well-structured code that handles all edge cases.
Is Phantom Code detectable when solving problems like Design an ATM Machine during live interviews?
No. Phantom Code runs as an invisible desktop overlay that doesn't appear in screen shares, recordings, or proctoring software. It works with Zoom, HackerRank, CodeSignal, CoderPad, and all major platforms.
How does Phantom Code help when I'm struggling with Design an ATM Machine style questions under pressure?
The AI provides structured guidance: first the approach (what algorithm/data structure to use and why), then the implementation with clean code, and finally complexity analysis. This helps you think clearly even under pressure.
Does Phantom Code work for the coding platforms used in Design an ATM Machine interviews?
Yes. Phantom Code works with all major coding platforms including LeetCode, HackerRank, CodeSignal, CoderPad, HackerEarth, and any browser-based coding environment.
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