HardText Processing

Repeated Word Detector

Write a regex that detects when the same word appears twice in a row separated by whitespace, such as 'the the' or 'is is', a common typo in written text.

//
the the cat sat / this is is a test / no repeats here / buffalo buffalo buffalo

Test cases

  • the the cat sat
  • this is is a test
  • no repeats here
  • buffalo buffalo buffalo
  • hello world
  • cat cats
  • she said said nothing

How to Solve this Regex Challenge

To complete the Repeated Word Detector challenge, you must write a regular expression pattern that satisfies all specified test cases.

Steps to Complete:

  1. Analyze the Requirements: Read the description and review the list of test cases below. Identify which strings must be matched (green markers) and which must be rejected (red markers).
  2. Draft Your Pattern: Enter your regex in the interactive editor. Use the provided Hint button if you get stuck.
  3. Verify: The test cases panel will update in real-time as you type, showing which strings match your current expression.
  4. Review the Solution: Once you successfully pass all test cases, review the explanation to understand the logic behind the solution.