Doubt in the question

#1

I am not able able to understand the solution can you please explain the procedure or dry run it

#2

@Adhyayan approach is similar to generating the subsequence of string.

e.g: 12

we have ques=123 so we get the first char ‘1’ as ch and the remaining 2 is stored as ros to be passed recursively now.then we find the code for ch i.e. 1 here so we get code as .+@$ and we append each char of .+@$ to ans so for the first loop we have ans as [.],[+],[@],[$]…now we recursively called the function for ros and ans which gives us abc appended to each ans individually
.a
.b
.c
+a
+b
+c
@a
@b
@c
$a
$b
$c