Grokking the Coding Interview: Patterns for Coding Questions
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Alien Dictionary (hard)

Problem Statement

There is a dictionary containing words from an alien language for which we don’t know the ordering of the letters. Write a method to find the correct order of the letters in the alien language. It is given that the input is a valid dictionary and there exists an ordering among its letters.

Example 1:

Input: Words: ["ba", "bc", "ac", "cab"]
Output: bac
Explanation: Given that the words are sorted lexicographically by the rules of the alien language, so
from the given words we can conclude the following ordering among its characters:





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