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Solution: Count Substrings With K-Frequency Characters II

Explore how to efficiently count substrings where at least one character appears exactly k times by applying the sliding window technique. Understand frequency tracking, window expansion and contraction, and how to optimize substring counting, preparing you to solve related interview problems effectively.

Statement

Given a string s and an integer k, return the total number of substrings of s where at least one character appears at least k times.

Note: A substring is a contiguous sequence of characters within a string. For example, "edu" is a substring of "educative". 

Constraints:

  • 11 \leq ...