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How to Solve Length of the Longest Valid Substring Problem
Master the Length of the Longest Valid Substring LeetCode problem with undetectable real-time assistance. Get instant solutions and explanations during your coding interviews.
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Start Free for WindowsHard#2781
LeetCode ProblemLength of the Longest Valid Substring
You are given a string word and an array of strings forbidden. A string is called valid if none of its substrings are present in forbidden. Return the length of the longest valid substring of the string word. A substring is a contiguous sequence of characters in a string, possibly empty.
ArrayHash TableStringSliding Window
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Problem Breakdown
Understanding the Length of the Longest Valid Substring Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
Problem Statement
You are given a string word and an array of strings forbidden. A string is called valid if none of its substrings are present in forbidden. Return the length of the longest valid substring of the string word. A substring is a contiguous sequence of characters in a string, possibly empty.
HardProblem #2781
LeetCodeLength of the Longest Valid Substring
Related Topics
ArrayHash TableStringSliding Window
How Phantom Code Helps
Get real-time assistance for Length of the Longest Valid Substring problems during coding interviews. Phantom Code provides instant solutions and explanations.
Examples
# Example 1
Input
word = "cbaaaabc", forbidden = ["aaa","cb"]
Output
4
# Example 2
Input
word = "leetcode", forbidden = ["de","le","e"]
Output
4
Constraints
1 <= word.length <= 105
word consists only of lowercase English letters.
1 <= forbidden.length <= 105
1 <= forbidden[i].length <= 10
forbidden[i] consists only of lowercase English letters.
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Solve Length of the Longest Valid Substring — You are given a string word and an array of strings forbidden. A string is calle...
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 Length of the Longest Valid Substring and using Phantom Code during coding interviews.
How does Phantom Code help me solve coding problems like Length of the Longest Valid Substring 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 Length of the Longest Valid Substring?
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 Length of the Longest Valid Substring?
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 Length of the Longest Valid Substring 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 Length of the Longest Valid Substring 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 Length of the Longest Valid Substring 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 Length of the Longest Valid Substring 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 Length of the Longest Valid Substring 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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