Write a shell script to concatenate lists together, and output the resulting list

Write a shell script to concatenate lists together, and output the resulting list. Do not include any argument that is a sub-list of the entire list. (The script will clean the list of any redundant items.) You must preserve the original order of the list. Remember to account for the following situations:
a : at the beginning of the list is the same as a . at the beginning of the "list" (:/bin is the same a .:/bin)
a :: any where in the list is the same as :.: (/bin::/etc is the same as (/bin:.:/etc)
a : at the end of the list is the same a :. ( /bin: is the same as /bin:. )
Project using temporary files will not be graded.
The input to the script will be color or space separated lists and the output will be a colon separated list with the original order preserved and all redundant items removed.