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How to Solve Inverse Coin Change Problem
Master the Inverse Coin Change LeetCode problem with undetectable real-time assistance. Get instant solutions and explanations during your coding interviews.
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Start Free for WindowsMedium#3592
LeetCode ProblemInverse Coin Change
You are given a 1-indexed integer array numWays, where numWays[i] represents the number of ways to select a total amount i using an infinite supply of some fixed coin denominations. Each denomination is a positive integer with value at most numWays.length. However, the exact coin denominations have been lost. Your task is to recover the set of denominations that could have resulted in the given numWays array. Return a sorted array containing unique integers which represents this set of denominations. If no such set exists, return an empty array.
ArrayDynamic Programming
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Problem Breakdown
Understanding the Inverse Coin Change Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
Problem Statement
You are given a 1-indexed integer array numWays, where numWays[i] represents the number of ways to select a total amount i using an infinite supply of some fixed coin denominations. Each denomination is a positive integer with value at most numWays.length. However, the exact coin denominations have been lost. Your task is to recover the set of denominations that could have resulted in the given numWays array. Return a sorted array containing unique integers which represents this set of denominations. If no such set exists, return an empty array.
MediumProblem #3592
LeetCodeInverse Coin Change
Related Topics
ArrayDynamic Programming
How Phantom Code Helps
Get real-time assistance for Inverse Coin Change problems during coding interviews. Phantom Code provides instant solutions and explanations.
Examples
# Example 1
Input
numWays = [0,1,0,2,0,3,0,4,0,5]
Output
[2,4,6]
# Example 2
Input
numWays = [1,2,2,3,4]
Output
[1,2,5]
# Example 3
Input
numWays = [1,2,3,4,15]
Output
[]
Constraints
1 <= numWays.length <= 100
0 <= numWays[i] <= 2 * 108
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Solve Inverse Coin Change — You are given a 1-indexed integer array numWays, where numWays[i] represents the...
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 Inverse Coin Change and using Phantom Code during coding interviews.
How does Phantom Code help me solve coding problems like Inverse Coin Change 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 Inverse Coin Change?
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 Inverse Coin Change?
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 Inverse Coin Change 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 Inverse Coin Change 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 Inverse Coin Change 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 Inverse Coin Change 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 Inverse Coin Change 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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