Given a string s, you can transform every letter individually to be lowercase or uppercase to create another string. Return a list of all possible strings you could create. Return the output in any order.
Example 1:
Input: s = "a1b2"
Output: ["A1B2","A1b2","a1B2","a1b2"]
Explanation: Each letter ('a' and 'b') can independently be uppercase or lowercase.
Example 2:
Input: s = "3z4"
Output: ["3Z4","3z4"]
Explanation: Only 'z' is a letter, so there are two possibilities.
Example 3:
Input: s = "12345"
Output: ["12345"]
Explanation: No letters in the string, so only one possibility.
1 <= s.length <= 12s consists of lowercase English letters, uppercase English letters, and digits