Good morning! Here's your coding interview problem for today.
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'].