Removing duplicates on a variable without sorting

Question

I have a variable that contains the following space separated entries.

variable=\"apple lemon papaya avocado lemon grapes papaya apple avocado mango banana\"         


        

Answer 1

Z Shell:

% variable="apple lemon papaya avocado lemon grapes papaya apple avocado mango banana"
% print ${(zu)variable}                                                               
apple lemon papaya avocado grapes mango banana