Substrings with k distinct characters
Given a string s of lowercase letters and an integer k (1 <= k <= 26, 1 <= len(s) <= 10^4), return the number of (contiguous) substrings that contain EXACTLY k distinct characters.
Implement
count_substrings_with_k_distinct(s: str, k: int) → intExamples
in
["pqpqs",2]out7What a strong answer looks like
State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.
0:00 of about 25 min
solution.py
InputExpectedGot
["pqpqs",2]7not run yetsample