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How to Solve Minimum Number of Valid Strings to Form Target II Problem
Master the Minimum Number of Valid Strings to Form Target II LeetCode problem with undetectable real-time assistance. Get instant solutions and explanations during your coding interviews.
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LeetCode ProblemMinimum Number of Valid Strings to Form Target II
You are given an array of strings words and a string target. A string x is called valid if x is a prefix of any string in words. Return the minimum number of valid strings that can be concatenated to form target. If it is not possible to form target, return -1.
ArrayStringBinary SearchDynamic ProgrammingSegment TreeRolling HashString MatchingHash Function
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Problem Breakdown
Understanding the Minimum Number of Valid Strings to Form Target II Problem
Let's break down this LeetCode problem and understand what makes it challenging in interview settings.
Problem Statement
You are given an array of strings words and a string target. A string x is called valid if x is a prefix of any string in words. Return the minimum number of valid strings that can be concatenated to form target. If it is not possible to form target, return -1.
HardProblem #3292
LeetCodeMinimum Number of Valid Strings to Form Target II
Related Topics
ArrayStringBinary SearchDynamic ProgrammingSegment TreeRolling HashString MatchingHash Function
How Phantom Code Helps
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Examples
# Example 1
Input
words = ["abc","aaaaa","bcdef"], target = "aabcdabc"
Output
3
# Example 2
Input
words = ["abababab","ab"], target = "ababaababa"
Output
2
# Example 3
Input
words = ["abcdef"], target = "xyz"
Output
-1
Constraints
1 <= words.length <= 100
1 <= words[i].length <= 5 * 104
The input is generated such that sum(words[i].length) <= 105.
words[i] consists only of lowercase English letters.
1 <= target.length <= 5 * 104
target consists only of lowercase English letters.
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Solve Minimum Number of Valid Strings to Form Target II — You are given an array of strings words and a string target. A string x is calle...
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def solve(input):
# Optimal O(n) solution
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Time: O(n) | Space: O(n)
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Frequently Asked Questions
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How does Phantom Code help me solve coding problems like Minimum Number of Valid Strings to Form Target II 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 Minimum Number of Valid Strings to Form Target II?
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.
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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 Minimum Number of Valid Strings to Form Target II 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 Minimum Number of Valid Strings to Form Target II 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 Minimum Number of Valid Strings to Form Target II 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 Minimum Number of Valid Strings to Form Target II 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 Minimum Number of Valid Strings to Form Target II 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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