Grokking 75: Top Coding Interview Questions
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Longest Substring with At Least K Repeating Characters (medium)
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Problem Statement

Given a string s and an integer k, return the maximum length of the substring where each character appears at least k times. If no such substring exists, return 0.

Examples

Example 1:

  • Input: s = "aaabbcc", k = 2
  • Output: 7
  • Justification: The longest substring is "aaabbcc", where each character ('a', 'b', and 'c') appears at least 2 times.

Example 2:

  • Input: s = "ababbc", k = 3
  • Output: 0
  • Justification: There is no substring exists having each character frequency at least 3.

Example 3:

  • Input: s = "abcdef", k = 1
  • Output: 6
  • Justification: The entire string "abcdef" is the longest substring, as each character appears at least once.

Constraints:

  • 1 <= s.length <= 10<sup>4</sup>
  • s consists of only lowercase English letters.
  • 1 <= k <= 10<sup>5</sup>

Try it yourself

Try solving this question here:

Python3
Python3
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