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How to Solve Sum of Good Subsequences Problem
Master the Sum of 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#3351
LeetCode ProblemSum of Good Subsequences
You are given an integer array nums. A good subsequence is defined as a subsequence of nums where the absolute difference between any two consecutive elements in the subsequence is exactly 1. Return the sum of all possible good subsequences of nums. Since the answer may be very large, return it modulo 109 + 7. Note that a subsequence of size 1 is considered good by definition.
ArrayHash TableDynamic Programming
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Problem Breakdown
Understanding the Sum of Good Subsequences Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
Problem Statement
You are given an integer array nums. A good subsequence is defined as a subsequence of nums where the absolute difference between any two consecutive elements in the subsequence is exactly 1. Return the sum of all possible good subsequences of nums. Since the answer may be very large, return it modulo 109 + 7. Note that a subsequence of size 1 is considered good by definition.
HardProblem #3351
LeetCodeSum of Good Subsequences
Related Topics
ArrayHash TableDynamic Programming
How Phantom Code Helps
Get real-time assistance for Sum of Good Subsequences problems during coding interviews. Phantom Code provides instant solutions and explanations.
Examples
# Example 1
Input
nums = [1,2,1]
Output
14
# Example 2
Input
nums = [3,4,5]
Output
40
Constraints
1 <= nums.length <= 105
0 <= nums[i] <= 105
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Solve Sum of Good Subsequences — You are given an integer array nums. A good subsequence is defined as a subseque...
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 Sum of Good Subsequences and using Phantom Code during coding interviews.
How does Phantom Code help me solve coding problems like Sum of 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 Sum of 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 Sum of 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 Sum of 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 Sum of 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 Sum of 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 Sum of 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 Sum of 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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