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Find Duplicate Words (Main Thread)

Here is the interview question prompt, presented for reference.

A very common interview challenge is to determine how often words appear in a given string or set of strings. Here's a version of this: return a list of duplicate words in a sentence.

For example, given 'The dog is the best', returns ["the"].

Likewise, given 'Happy thanksgiving, I am so full', you would return an empty array. This is because there are no duplicates in the string.


  • The total length of the string <= 100000
  • The string will consist of ASCII characters (may be some or all)
  • Expected time complexity : O(n) where n are the number of words in the string
  • Expected space complexity : O(n)

You can see the full challenge with visuals at this link.

Challenges • Asked about 3 years ago by Anonymous

Jake from AlgoDaily Commented on Apr 08, 2020:

This is the main discussion thread generated for Find Duplicate Words.

Anonymous Commented on Apr 08, 2020:


int2k Commented on Oct 29, 2022:

hi How can I submit this with several other tests? I only found "run code".

In addition to that, when I click on "Your submission", the page turns blank

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