No adjacent equal digits
Count integers n in [1, N] whose decimal representation has no two adjacent equal digits (e.g. 121 is fine, 122 is not). N can be up to about 10^15. Leading zeros are not part of the number, so the constraint applies only to actual digits.
Implement
count_no_adjacent_equal(N: int) → intExamples
in
[20]out19What 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
[20]19not run yetsample