Decode ways
A message of digits is encoded by mapping 'A'->1, 'B'->2, ..., 'Z'->26. Given a non-empty digit string, return the number of ways to decode it back into letters. A valid single digit is 1-9 and a valid two-digit group is 10-26; a leading '0' in a group is invalid. The string length is at most 100.
Implement
num_decodings(s: str) → intExamples
in
["226"]out3What 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
["226"]3not run yetsample