How to solve "No Prefix Set" on HackerRank

T he challenge is figure out whether any string in a set is a prefix of any other string, and if so, to print the first string in the set which either is the prefix of a previous string, or of which a previous string is a prefix. And, as with many other HackerRank challenges, the real challenge is to do it efficiently. Fortunately, in this case, the solution is simple: a data structure called a…