Digit sum 0 to n
Return the sum of the decimal digits of every integer from 0 to n inclusive. For n=12 the answer is 0+1+2+...+9+1+(1+0)+(1+1)+(1+2) = 51. 0 <= n <= 10^12. Use an approach that does not iterate over every integer.
Implement
digit_sum_upto(n: int) → intExamples
in
[12]out51What 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 35 min
solution.py
InputExpectedGot
[12]51not run yetsample