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Solution: Count Substrings With K-Frequency Characters II

Explore a sliding window technique to efficiently count substrings in a string where at least one character appears exactly k times. Understand how to maintain character frequency counts and adjust window boundaries to solve the problem in linear time and constant space complexity.

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 ...