Grokking the Coding Interview: Patterns for Coding Questions
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Problem Challenge 4: Words Concatenation (hard)
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Problem Statement

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Problem Statement

You’re given a string s and a list of words words, where all words have the same length.

A concatenated substring is formed by joining all the words from any permutation of words — each used exactly once, without any extra characters in between.

For example, if words = ["ab", "cd", "ef"], then valid concatenated strings include "abcdef", "abefcd", "cdabef", "cdefab", "efabcd", and "efcdab". A string like "acdbef" is not valid because it doesn't match any complete permutation of the given words.

Return all starting indices in s where such concatenated substrings appear. You can return the indices in any order.

Example 1:

Input: String="catfoxcat", Words=["cat", "fox"]  
Output: [0, 3]  
Explanation: The two substring containing both the words are "catfox" & "foxcat".

Example 2:

Input: String="catcatfoxfox", Words=["cat", "fox"]  
Output: [3]
Explanation: The only substring containing both the words is "catfox".

Constraints:

  • 1 <= words.length <= 10<sup>4</sup>
  • 1 <= words[i].length <= 30
  • words[i] consists of only lowercase English letters.
  • All the strings of words are unique.
  • 1 <= sum(words[i].length) <= 10<sup>5</sup>

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Python3
Python3
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Problem Statement

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