Digit sum divisibility count
Count how many integers x in the inclusive range [lo, hi] have a digit sum that is divisible by a given modulus k. Return the count. Constraints: 0 <= lo <= hi <= 10**18, 1 <= k <= 100. A brute-force loop over the range is far too slow; use digit DP with a prefix-count(hi) - prefix-count(lo-1) approach.
Implement
count_digit_sum_divisible(lo: int, hi: int, k: int) → intExamples
in
[1,20,3]out6What 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 30 min
solution.py
InputExpectedGot
[1,20,3]6not run yetsample