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Solution: Count Substrings With K-Frequency Characters II

Explore how to solve substring frequency problems with the sliding window approach. Understand how to track character frequencies and count valid substrings efficiently in linear time using two pointers, optimizing both time and 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 ...