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Solution: Count Substrings With K-Frequency Characters II

Explore the sliding window technique to solve substring problems efficiently, focusing on counting substrings where at least one character appears at least k times. Learn how to manage character frequencies dynamically and optimize your approach to achieve O(n) time complexity with constant space usage.

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 ...