Search⌘ K
AI Features

Solution: Count Substrings With K-Frequency Characters II

Explore how to efficiently count the total number of substrings with at least one character appearing k times using the sliding window technique. Understand the use of two pointers, frequency arrays, and window adjustments to optimize the solution with linear time complexity and constant space, suitable for handling large strings 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 s.length 3×103\leq 3 \times 10^{3}

  • 11 \leq k ...