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How to Solve Number of Unique Good Subsequences Problem
Master the Number of Unique Good Subsequences LeetCode problem with undetectable real-time assistance. Get instant solutions and explanations during your coding interviews.
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Start Free for WindowsHard#1987
LeetCode ProblemNumber of Unique Good Subsequences
You are given a binary string binary. A subsequence of binary is considered good if it is not empty and has no leading zeros (with the exception of "0"). Find the number of unique good subsequences of binary. Return the number of unique good subsequences of binary. Since the answer may be very large, return it modulo 109 + 7. A subsequence is a sequence that can be derived from another sequence by deleting some or no elements without changing the order of the remaining elements.
StringDynamic Programming
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Problem Breakdown
Understanding the Number of Unique Good Subsequences Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
Problem Statement
You are given a binary string binary. A subsequence of binary is considered good if it is not empty and has no leading zeros (with the exception of "0"). Find the number of unique good subsequences of binary. Return the number of unique good subsequences of binary. Since the answer may be very large, return it modulo 109 + 7. A subsequence is a sequence that can be derived from another sequence by deleting some or no elements without changing the order of the remaining elements.
HardProblem #1987
LeetCodeNumber of Unique Good Subsequences
Related Topics
StringDynamic Programming
How Phantom Code Helps
Get real-time assistance for Number of Unique Good Subsequences problems during coding interviews. Phantom Code provides instant solutions and explanations.
Examples
# Example 1
Input
binary = "001"
Output
2
# Example 2
Input
binary = "11"
Output
2
# Example 3
Input
binary = "101"
Output
5
Constraints
1 <= binary.length <= 105
binary consists of only '0's and '1's.
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Solve Number of Unique Good Subsequences — You are given a binary string binary. A subsequence of binary is considered good...
Here's the optimal approach using String:
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 Number of Unique Good Subsequences and using Phantom Code during coding interviews.
How does Phantom Code help me solve coding problems like Number of Unique Good Subsequences 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 Number of Unique Good Subsequences?
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 Number of Unique Good Subsequences?
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 Number of Unique Good Subsequences 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 Number of Unique Good Subsequences 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 Number of Unique Good Subsequences 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 Number of Unique Good Subsequences 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 Number of Unique Good Subsequences 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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