Implementation Difficulty in String Problem

general
,
1

Please see here

2

I can tell you only pseudo code

Here it is:

If there is no question mark
print -1

If there is a question mark and all the alphabets have been used then again
print -1

else if there is a question mark and all the alphabets have not been used and you can fill those without repeating any of them then
print random alphabets

Happy Coding!