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How to Solve Additive Number Problem
Master the Additive Number LeetCode problem with undetectable real-time assistance. Get instant solutions and explanations during your coding interviews.
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Start Free for WindowsMedium#306
LeetCode ProblemAdditive Number
An additive number is a string whose digits can form an additive sequence. A valid additive sequence should contain at least three numbers. Except for the first two numbers, each subsequent number in the sequence must be the sum of the preceding two. Given a string containing only digits, return true if it is an additive number or false otherwise. Note: Numbers in the additive sequence cannot have leading zeros, so sequence 1, 2, 03 or 1, 02, 3 is invalid. Example 1: Example 2: Constraints: Follow up: How would you handle overflow for very large input integers?
StringBacktracking
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Problem Breakdown
Understanding the Additive Number Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
Problem Statement
An additive number is a string whose digits can form an additive sequence. A valid additive sequence should contain at least three numbers. Except for the first two numbers, each subsequent number in the sequence must be the sum of the preceding two. Given a string containing only digits, return true if it is an additive number or false otherwise. Note: Numbers in the additive sequence cannot have leading zeros, so sequence 1, 2, 03 or 1, 02, 3 is invalid. Example 1: Example 2: Constraints: Follow up: How would you handle overflow for very large input integers?
MediumProblem #306
LeetCodeAdditive Number
Related Topics
StringBacktracking
How Phantom Code Helps
Get real-time assistance for Additive Number problems during coding interviews. Phantom Code provides instant solutions and explanations.
Examples
# Example 1
Input
"112358"
Output
true
# Example 2
Input
"199100199"
Output
true
Constraints
1 <= num.length <= 35
num consists only of digits.
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Solve Additive Number — An additive number is a string whose digits can form an additive sequence. A val...
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 Additive Number and using Phantom Code during coding interviews.
How does Phantom Code help me solve coding problems like Additive Number 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 Additive Number?
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 Additive Number?
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 Additive Number 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 Additive Number 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 Additive Number 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 Additive Number 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 Additive Number 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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