Longest Substring K Distinct

Python data engineering interview problem. Difficulty: intermediate. Pattern: Sliding Window. About 14 minutes. Part of the Pro drill bank.

Longest substring with at most k distinct characters. Treat this as a production helper: match the contracted return shape, including empty and duplicate inputs.

Implement length_k_distinct(s: str, k: int) -> int. ("ece").

Requirements

• Max length with <= k distinct chars.

Constraints

• k may be 0 (then answer is 0).
• Lowercase letters.

Examples

Input: length_k_distinct('eceba', 2) Output: 3 ece uses two distinct letters.

Topics: lakebench, python, window, k-distinct.

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