17 Nov Aurora Saturday 14:30 Python Practice 20.11.14.
A collection of words is prefix-free if no word is a prefix of any other word. A collection of words is suffix-free if no word is a suffix of any other word. A collection of words is fix-free if it is both prefix-free and suffix-free.
For this problem, a word is a sequence of lower-case letters of length between 1 and 25. A word X is a prefix of word Y if X consists of the first n characters of Y, in order, for some n. That is, the word cat has prefixes c, ca, and cat. Similarly, a word X is a suffix of Y if X consists of the last n characters of Y, in order, for some n.
Your input will be 3N+1 lines: the first line will be the number N, and the remaining 3N lines will be the N collections of 3 words each. (That is, lines 2, 3, and 4 compose the first collection, lines 5, 6, and 7 compose the second collection, and so on). Your output will be N lines, each line containing either Yes (if that collection of words is fix-free) or No (if that collection is not fix-free).