Letter case permutations
Your task
Given a string s (length 1..12) of letters and digits, you may transform every letter into either lowercase or uppercase (digits are unchanged). Return all strings that can be created this way, sorted ascending. The number of outputs is 2 raised to the number of letters in s.
Examples
letter_case_permutation(s: str) -> list[str]Example 1
Input
letter_case_permutation("a1b2")Output
["A1B2", "A1b2", "a1B2", "a1b2"]