Is it guaranteed that answer exists?

Does a solution guaranteed to be exist?

I'm converting the prefix notation to infix and then counting the positives and the negatives. Getting TLE for the last 2 cases. Can someone tell why?

in test case : +--???--??? My Output is : 1 1 1 3 1 1

<=> (1-1-1) + (3-1-1) = 0 Why i get WA???

why not 311111 for +--???--???

 + - - 3 1 1 - - 1 1 1
 + - (3-1) 1 - (1-1) 1
 + (2-1) (0-1)
 (1 + (-1))
 0

Says wrong output!