Problem C: Catenyms
A catenym is a pair of words separated by a period such that the last letter of
the first word is the same as the last letter of the second. For example, the
following are catenyms:
dog.gopher
gopher.rat
rat.tiger
aloha.aloha
arachnid.dog
A compound catenym is a sequence of three or more words separated by periods such
that each adjacent pair of words forms a catenym. For example,
aloha.aloha.arachnid.dog.gopher.rat.tiger
Given a dictionary of lower case words, you are to find a
compound catenym
that contains each of the words exactly once. The first line of standard input
contains t, the number of test cases. Each test case begins with
3 <= n <= 1000 - the number of words in the dictionary. n
distinct dictionary words follow; each word is a string of between 1 and 20
lowercase letters on a line by itself. For each test case, output a line
giving the lexicographically least compound catenym that contains
each dictionary word exactly once. Output "***" if there is no solution.
Sample Input
2
6
aloha
arachnid
dog
gopher
rat
tiger
3
oak
maple
elm
Output for Sample Input
aloha.arachnid.dog.gopher.rat.tiger
***