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+%22%22%22Leetcode 269. Alien Dictionary%0AHard%0A%0AURL: https://leetcode.com/problems/alien-dictionary%0A%0AThere is a new alien language which uses the latin alphabet. However, the order%0Aamong letters are unknown to you. You receive a list of non-empty words from%0Athe dictionary, where words are sorted lexicographically by the rules of this%0Anew language. Derive the order of letters in this language.%0A%0AExample 1:%0AInput:%0A%5B%0A  %22wrt%22,%0A  %22wrf%22,%0A  %22er%22,%0A  %22ett%22,%0A  %22rftt%22%0A%5D%0AOutput: %22wertf%22%0AExample 2:%0AInput:%0A%5B%0A  %22z%22,%0A  %22x%22%0A%5D%0AOutput: %22zx%22%0A%0AExample 3:%0AInput:%0A%5B%0A  %22z%22,%0A  %22x%22,%0A  %22z%22%0A%5D %0AOutput: %22%22 %0AExplanation: The order is invalid, so return %22%22.%0A%0ANote:%0A- You may assume all letters are in lowercase.%0A- You may assume that if a is a prefix of b, then a must appear before b in the %0A  given dictionary.%0A- If the order is invalid, return an empty string.%0A- There may be multiple valid order of letters, return any one of them is fine.%0A%22%22%22%0A%0Aclass Solution(object):%0A    def alienOrder(self, words):%0A        %22%22%22%0A        :type words: List%5Bstr%5D%0A        :rtype: str%0A        %22%22%22%0A        pass%0A%0A%0Adef main():%0A    pass%0A%0A%0Aif __name__ == '__main__':%0A    main()%0A

Add lc0269_alien_dictionary.py