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Clarify a Longest-Repeating-Character Replacement Problem

DigitaloceanSoftware Engineer · Onsite
MediumSoftware EngineerOnsiteSoftware Engineering Fundamentals

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Clarify replacement and substring semantics, then analyze the conditional sliding-window criterion based on window size and maximum character frequency.

Discuss how to specify and solve a longest-repeating-character replacement problem. Clarify the replacement operation and the target segment before selecting an algorithm.

Constraints

The supplied task name does not define the alphabet, replacement budget, whether the target must be contiguous, or what output is required. Treat the following as an illustrative variant only: at most k single-character substitutions may be used to make a contiguous substring contain one repeated character, and the output is its maximum length. Do not assume this is the only possible contract.

Clarifying Questions

  • Does one replacement change exactly one character, and is the budget at most k or exactly k?
  • Must the chosen characters form a contiguous substring or only a subsequence?
  • Is the target repeated character fixed or chosen freely?
  • Are we returning a length, positions, or a transformed string, and what is the alphabet?

Hints

Hint 1

Count what must change inside a candidate window: For a freely chosen target character, keeping the most frequent character minimizes how many other positions need replacement.

Follow-up questions

  • How does the condition change when the target character is fixed?
  • Why would a subsequence interpretation change the role of a sliding window?