problem_226.js

// This problem was asked by Airbnb.

// You come across a dictionary of sorted words in a language you've never seen before. Write a program that returns the correct order of letters in this language.

// For example, given ['xww', 'wxyz', 'wxyw', 'ywx', 'ywz'], you should return ['x', 'z', 'w', 'y'].